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Does rituximab increase the incidence of infectious complications? A narrative review

International Journal of Infectious Diseases, 1, 15, pages e2 - e16

Abstract

Background: Rituximab has increasingly been used for the treatment of hematological malignancies and autoimmune diseases, and its efficacy and safety are well established. Although clinical trials have shown conflicting results regarding the association of rituximab with infections, an increased incidence of infections has recently been reported in patients with lymphomas being treated with rituximab. However, clinical experience regarding the association of rituximab with different types of infection is lacking and this association has not been established in patients with rheumatoid arthritis.

Methods: All previous studies included in our literature review were found using a PubMed, EMBASE, and Cochrane database search of the English-language medical literature applying the terms ‘rituximab’, ‘monoclonal antibodies’, ‘infections’, ‘infectious complications’, and combinations of these terms. In addition, the references cited in these articles were examined to identify additional reports.

Results: We performed separate analyses of data regarding the association of rituximab with infection in (1) patients with hematological malignancies, (2) patients with autoimmune disorders, and (3) transplant patients. Recent data show that rituximab maintenance therapy significantly increases the risk of both infection and neutropenia in patients with lymphoma or other hematological malignancies. On the other hand, data available to date do not indicate an increased risk of infections when using rituximab compared with concurrent control treatments in patients with rheumatoid arthritis. However, there is a lack of sufficient long-term data to allow such a statement to be definitively made, and caution regarding infections should continue to be exercised, especially in patients who have received repeated courses of rituximab, are receiving other immunosuppressants concurrently, and in those whose immunoglobulin levels have fallen below the normal range. Few data are available concerning the risk of organ transplant recipients developing infections following rituximab therapy. Data from case reports, case series, and retrospective studies correlate rituximab use with the development of a variety of infections in transplant patients.

Conclusions: Further studies are needed to clarify the association of rituximab with infection. Physicians and patients should be educated about the association of rituximab with infectious complications. Monitoring of absolute neutrophil count and immunoglobulin levels and the identification of high-risk groups for the development of infectious complications, with timely vaccination of these groups, are clearly needed.

Abbreviations: CHOP - cyclophosphamide doxorubicin vincristine and prednisone, CLL - chronic lymphocytic leukemia, CVP - cyclophosphamide, vincristine, and prednisone, CI - confidence intervals, CMV - cytomegalovirus, CNS - central nervous system, DLBCL - diffuse large B-cell lymphoma, dcSSc - diffuse cutaneous systemic sclerosis, DMARD - Disease Modifying Antirheumatic Drug, EBV - Epstein Barr Virus, FDA - Food and Drug Administration, FCM - fludarabine, cyclophosphamide, and mitoxantrone, G-CSF - Granulocyte Colony Stimulating Factor, HIV - Human Immunodeficiency Virus, HBV - Hepatitis B virus, HCV - Hepatitis C virus, HEV - Hepatitis E virus, HbsAg - Hepatitis B surface antigen, HDMP - High dose methylprednisolone, HIV - human immunodeficiency virus, HSV - Herpes Simplex Virus, HSCT - hematological stem cell transplantation, MTX - methotrexate, MCP - mitoxantrone, chlorambucil, and prednisolone, ND - Not determined, NHL - non-Hodgkin lymphoma, NR - not reported, OI - Opportunistic infections, PCP - Pneumocystis Carinii Pneumonia, PML - progressive multifocal leucoencephalopathy (PML), R - rituximab, RA - rheumatoid arthritis, RCT - randomized controlled trial, RR - relative risk, RSV - respiratory syncytial virus, SL - small lymphocytic lymphoma, SIE - serious infection events, SLE - systematic lupus erythematosus, TNF - tumor necrosis factor), VZV - Varicella Zoster Virus.

Keywords: Rituximab, Infection, Immunocompromised.

KEY POINTS

  • Clinical trials have shown conflicting results regarding the association of rituximab with infections. However, clinical experience regarding the association of rituximab with different types of infection is lacking.
  • An increased incidence of infections in patients with lymphomas and rheumatoid arthritis being treated with rituximab has been recently reported.
  • Education of physicians and patients about the association of rituximab with infectious complications, monitoring of absolute neutrophil count and immunoglobulin levels, identification of high risk groups for development of infectious complications and timely vaccination of these groups are needed

1. Introduction

Rituximab (Rituxan®) is a chimeric human–mouse monoclonal antibody that has been used extensively in the treatment of hematological malignancies and autoimmune diseases and is US Food and Drug Administration (FDA) approved for CD20-positive B-cell non-Hodgkin's lymphoma (NHL) and for moderate-to-severe rheumatoid arthritis (RA) not responding to other treatments.1, 2, and 3 More specifically, rituximab is a human–mouse chimeric monoclonal antibody (IgG1) that reacts specifically with the CD20 antigen expressed on more than 95% of normal and malignant B-cells, inducing complement-mediated and antibody-dependent cellular cytotoxicity ( Fig. 1 ). 4

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Fig. 1 Mechanism of action of rituximab. Rituximab reacts specifically with the CD20 antigen expressed on more than 95% of normal and malignant B-cells, inducing complement-mediated and antibody-dependent cellular cytotoxicity. There is growing evidence supporting the notion that rituximab, in addition to its effect on B cells, also influences T-cell immunity and this may predispose to opportunistic infections. Rituximab may in addition cause immunosuppression through several other mechanisms such as delayed-onset cytopenia, particularly neutropenia and hypogammaglobulinemia.

Treatment with rituximab causes a rapid depletion of pre-B- and mature B-cells, which remain at low or undetectable levels for 2–6 months before returning to pretreatment levels, generally within 12 months. There is growing evidence, including an increased incidence of certain viral infections with the use of rituximab, 5 supporting the notion that rituximab, in addition to its effect on B cells, also influences T-cell immunity and predisposes to opportunistic infections.6, 7, 8, and 9 Rituximab may cause immunosuppression through several other mechanisms such as delayed-onset cytopenia, particularly neutropenia 10 and hypogammaglobulinemia, especially when administered for long periods, e.g., in maintenance therapy.11, 12, and 13

Clinical trials have shown conflicting results regarding the association of rituximab with infections.5, 14, 15, 16, 17, 18, 19, 20, 21, and 22 An increased incidence of infections in patients with lymphomas and RA being treated with rituximab has recently been reported.23, 24, 25, and 26 Pooled data from 356 patients who received rituximab monotherapy showed that the incidence rate of infectious events was 30%; 19% of patients had bacterial infections, 10% viral infections, 1% fungal infections, and 6% infections of unknown etiology. Severe infections, including sepsis, occurred in only 1% of patients during the treatment period, and in 2% during the follow-up period. 15 In a recent review 27 involving 389 patients from 25 studies, the incidence of serious infections varied from 2.8% to 45% (mean 12.5%).

Infection in patients treated with rituximab is a multifactorial process and its incidence becomes difficult to analyze. The age of the patient, the presence of other medical problems, and concomitant drug therapies can influence susceptibility to infection. Thus, and for purposes of clarity, in this report we present separate data regarding the association of rituximab with infection in (1) patients with hematological malignancies, (2) patients with autoimmune disorders, and (3) transplant patients.

2. Methods

All previous studies included in our literature review were found using a search of PubMed, EMBASE, and the Cochrane database (through August 2009) of the English-language medical literature applying the terms ‘rituximab’, ‘monoclonal antibodies’, ‘infections’, ‘infectious complications’, and combinations of these terms. In addition, the references cited in these articles were examined to identify additional reports. Regarding the association of rituximab with infection, we reviewed evidence from meta-analyses, randomized controlled trials, and retrospective studies. We performed separate analyses of the data regarding the association of rituximab with infection in (1) patients with hematological malignancies, (2) patients with autoimmune disorders, and (3) transplant patients. However, due to the paucity of data regarding the different types of infections associated with the use of rituximab (bacterial, viral, fungal, parasitic), we also reviewed the evidence from case–control studies, case series, and case reports.

3. Rituximab and infection in hematological malignancies

Table 1 outlines the most important studies evaluating infection in rituximab-treated patients with hematological malignancies.19, 23, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, and 45

Table 1 Studies regarding infectious complications in patients with lymphoma treated with rituximab

Type of study Author, year [Ref.] Patient characteristics Chemotherapy Comments Outcome
Meta-analysis Aksoy, 2009 [23] Lymphoma Rituximab maintenance therapy Significantly increased rates of infections and neutropenia. Infection rates were 8.1% in patients who had received rituximab maintenance therapy vs. 3.9% in those who had not. Neutropenia rates were 13.4% vs. 6.3%, respectively (p < 0.001) Meta-analysis of the RCTs demonstrated that rituximab maintenance therapy significantly increased the RR of both infection and neutropenia in patients with lymphoma
Meta-analysis of RCTs Vidal, 2009 [28] Follicular lymphoma Rituximab Patients undergoing rituximab maintenance therapy had more infection-related adverse events than patients in the observation arm (RR 1.99, 95% CI 1.21–3.27). When only grade 3 or 4 infection-related adverse events were included in the analysis, this effect was even more pronounced (RR 2.90, 95% CI 1.24–6.76)  
RCT phase II Eve, 2009 [29] Previously untreated mantle cell lymphoma Fludarabine and cyclophosphamide with or without rituximab Non-hematological toxicity was similar between the two treatment arms  
RCT Kaplan, 2005 [30] NHL (HIV patients) R-CHOP vs. CHOP 99 patients treated with R-CHOP vs. 51 patients treated with CHOP (infection rate NR). Presence of opportunistic infections in the R-CHOP group and absence of these infections in the CHOP group Infection-related death was 14% with R-CHOP vs. 2% with CHOP (p  =  0.035)
RCT Lenz, 2005 [31] NHL Mantle cell R-CHOP vs. CHOP 33% (grade I–II) and 5% (grade III/IV) of 62 patients treated with R-CHOP developed infections vs. 29% (grade I–II) and 6% (grade III/IV) of 60 patients treated with CHOP NR
RCT Hiddemann, 2005 [32] NHL follicular R-CHOP vs. CHOP 5% of 223 patients treated with R-CHOP developed infections vs. 7% of 205 patients treated with CHOP Infection-related death 1.9% with R-CHOP vs. 0.5% with CHOP
RCT Feugier, 2005 [33], Coiffier, 2002 [34] DLBCL R-CHOP vs. CHOP 65% (any grade) and 12% (grade III/IV) of 202 patients treated with R-CHOP developed infections vs. 65% (any grade) and 20% (grade III/IV) of 197 patients treated with CHOP Infection-related death 1.7% with R-CHOP vs. 1.9% with CHOP
RCT Habermann, 2006 [35] DLBCL R-CHOP vs. CHOP 17% of 318 patients treated with R-CHOP developed infections vs. 16% of 314 patients treated with CHOP  
RCT Pfreundschuh, 2006 [36] NHL B-cell R-CHOP vs. CHOP 7% of 411 patients treated with R-CHOP developed infections vs. 8% of 413 patients treated with CHOP  
RCT Forstpointner, 2004 [37] NHL follicular and mantle cell Rituximab + FCM vs. FCM 1.5% (grade III/IV) of 62 patients treated with R-FCM developed infections vs. 1.5% (grade III/IV) of 66 patients treated with FCM  
RCT Marcus, 2005 [38] NHL follicular Rituximab + CVP vs. CVP No difference between the two groups (162 patients in R-CVP vs. 159 in CVP)  
RCT Herold, 2003 [39] Indolent NHL Rituximab + MCP vs. MCP No difference in infection rates between the two groups (55 patients in R-MCP vs. 51 in MCP)  
Controlled clinical trial Dungarwalla, 2008 [40] 14 heavily pre-treated CLL patients HDMP ± rituximab 2 cases of systemic candidiasis, 2 cases of aspergillosis, 1 case of VZV, 1 case of adenovirus, bacteremia. Although HDMP-R causes little or no myelosuppression, the addition of rituximab might have predisposed to opportunistic infections. However, heavily pre-treated CLL patients have an increased susceptibility to infection intrinsic to the disease. Small series of patients/caution about conclusions All patients died (except for the case with VZV)
RCT phase II Del Poeta, 2008 [41] B-CLL Fludarabine and rituximab 3 dermatomal herpes zoster infections and 4 localized herpes simplex infections  
Retrospective study Ennishi, 2008 [42] 64 yo M with follicular lymphoma stage IVa (partial response to treatment); 61 yo M with diffuse large B-cell lymphoma stage 1a (complete response to treatment) R-CHOP 13 of 90 (14%) patients developed interstitial pneumonitis during R-CHOP therapy, compared with none of 105 patients treated with CHOP alone; 2 of these cases were PCP All patients responded well to treatment, and recovered within 2–3 weeks
Retrospective study Lee, 2008 [19] 46 patients with relapsed indolent or high-risk aggressive B cell NHL who received rituximab (17 patients) or not (29 patients) before autologous HSCT Rituximab Post-transplant infectious complications up to 6 months after transplantation. Seventeen of 46 patients received rituximab before HSCT. Three of them suffered from CMV infection and two of them developed CMV disease. All of the patients with CMV disease recovered after ganciclovir and CMV-specific immunoglobulin therapy. Twenty-nine of 46 patients without rituximab treatment before HSCT did not develop CMV after HSCT. Risk of CMV infection after autologous HSCT higher in rituximab-treated patients (17.6% vs. 0%, p  =  0.045). Risk of CMV disease had higher trend with rituximab therapy than without rituximab therapy (11.7% vs. 0%, p  =  0.131) All 3 cases responded to ganciclovir combined with CMV-specific immunoglobulin
RCT phase III Van Oers, 2006 [43] Relapsed/resistant follicular lymphoma R-CHOP Upper respiratory tract infections mostly  
RCT phase III Ghielmini, 2005 [44] Mantle cell lymphoma R-CHOP One patient experienced three episodes of pneumonia, 1 case of hepatitis, 1 case of septic shock  
RCT phase II Hainsworth, 2003 [45] CLL/SL   Staphylococcus aureus pneumonia, 1 patient; localized herpes zoster, 1 patient; and gastroenteritis, probably viral, 1 patient  

CHOP, cyclophosphamide, doxorubicin, vincristine, and prednisone; CLL, chronic lymphocytic leukemia; CVP, cyclophosphamide, vincristine, and prednisone; CMV, cytomegalovirus; DLBCL, diffuse large B-cell lymphoma; FCM, fludarabine, cyclophosphamide, and mitoxantrone; HDMP, high-dose methylprednisolone; HIV, human immunodeficiency virus; HSCT, hematological stem cell transplantation; M, male; MCP, mitoxantrone, chlorambucil, and prednisolone; NHL, non-Hodgkin lymphoma; NR, not reported; PCP, Pneumocystis jiroveci (carinii) pneumonia; R, rituximab; RCT, randomized controlled trial; RR, relative risk; SL, small lymphocytic lymphoma; VZV, varicella zoster virus; yo, year-old.

In a recent systematic review in patients with lymphoma, Aksoy et al. found significantly increased rates of infections and neutropenia in patients who had received rituximab maintenance therapy compared with those who had not (8.1% vs. 3.9% and 13.4% vs. 6.3%, respectively). 23 In a similar meta-analysis of randomized controlled trials (RCT), patients with follicular lymphoma who underwent rituximab maintenance therapy had more infection-related adverse events than patients in the observation arm (relative risk (RR) 1.99, 95% confidence interval (CI) 1.21–3.27). 28 This effect was more pronounced when only grade 3 or 4 infection-related adverse events were included in the analysis (RR 2.90, 95% CI 1.24–6.76). 28

Regarding other hematological neoplasias, seven clinical trials tested rituximab added to the combination of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) versus CHOP chemotherapy alone. 26 In six studies comparing rituximab with CHOP (R-CHOP) versus CHOP alone (excluding HIV-1-positive patients), the rate of infection was higher in one study, 35 comparable in three studies,31, 32, and 36 and smaller in one study; 34 a 1% increase in infection-associated mortality was found in one study. 33

In HIV patients with lymphoma treated with R-CHOP versus CHOP, a significant 12% increase in the occurrence of opportunistic infections and infection-related deaths was observed. 30 Therefore, it appears that HIV seropositivity influences the incidence of infectious complications in such patients.

Concerning the combination of rituximab with non-CHOP-containing regimens, no significant difference in infection rates compared to the standard regimen was found in three RCTs.37, 38, and 39 Nevertheless, such effects depend on the co-administered agent. For example a combined regimen with fludarabine (associated with profound T-cell depletion) may substantially increase the risk of opportunistic infections both in the induction and the maintenance phase.37, 41, 46, and 47

The duration of rituximab therapy may also be important. In one retrospective study of hematology patients receiving rituximab, duration of rituximab therapy, reduction in IgM after administration of rituximab, and granulocyte colony-stimulating factor (G-CSF) administration were risk factors associated with infection. 48

Thus, rituximab significantly increases the risk of both infection and neutropenia in patients with lymphoma or other hematological malignancies, and this risk appears also to depend on the co-administered agent.

4. Rituximab and infection in autoimmune disorders

Table 2 outlines the most important studies evaluating infection in rituximab-treated patients with autoimmune disorders.24, 25, 49, 50, 51, 52, 53, 54, and 55

Table 2 Clinical trials and open label studies that report incidence of infections with use of rituximab in patients with rheumatoid arthritis

Type of study Author, year [Ref.] Patient characteristics Immunosuppression F/u of study duration Comments Outcome
Clinical trial Lafyatis, 2009 [49] Diffuse cutaneous systemic sclerosis Rituximab 6 months No significant infections were noted in this pilot study Treatment with rituximab appeared to be safe and well tolerated among patients with dcSSc
Clinical trial Genovese, 2009 [50] Patients with advanced RA many of whom had previously been treated with multiple RA therapies, including biologicals prior to receiving rituximab, and then withdrew from clinical trials and subsequently received further biological therapy Biological DMARD after rituximab treatment   In 185 patients who received rituximab plus another biological DMARD 13 SIEs (6.99 events/100 patient-years) occurred following rituximab, but prior to another biological DMARD. 10 SIEs (5.49 events/100 patient-years) occurred following another biological DMARD. SIEs were of typical type and severity for RA patients. No fatal or opportunistic infections The size of the sample and limited follow-up restricts definitive conclusions about safety in B-cell depleted patients receiving additional biological DMARDs
DANCER RCT (phase IIB) Emery, 2006 [51] Patients with RA MTX +/- rituximab 24 weeks 42/149 (28%) of patients who were treated with MTX developed infections and 2/149 (1%) developed serious infections. 50/142 (35%) of patients who were treated with MTX + rituximab (500 mg) developed infections and 0/142 (0%) developed serious infections. 67/192 (35%) of patients who were treated with MTX + rituximab (1000 mg) developed infections and 4/192 (2%) developed serious infections. Type and severity of infections were similar across all three treatment arms. The most common infections were respiratory tract infections, urinary tract infections, and nasopharyngitis. The overall rate of serious infections (events/100 patient-years) was 3.19 for MTX alone and 4.74 for rituximab 1000 mg Of the 6 serious infections, 2 occurred in the MTX monotherapy group (1 each of pneumonia and respiratory tract infection) and 4 occurred in the rituximab 1000 mg group (2 cases of pyelonephritis and 1 case each of bronchitis and epiglottitis); all serious infections were reported to have resolved without sequelae
Phase IIA Edwards, 2004 [52] Patients with RA MTX +/- rituximab, cyclophosphamide + rituximab 24 weeks 1/40 (3%) of patients who were treated with MTX developed serious infections. 2/40 (5%) of patients who were treated with rituximab (1000 mg) developed serious infections. 2/41 (5%) of patients who were treated with cyclophosphamide + rituximab (1000 mg) developed serious infections. 0/40 (0%) of patients who were treated with MTX + rituximab (1000 mg) developed serious infections. In total 4 patients who had received rituximab developed serious infections (2 had septic arthritis, 1 of whom also had Staphylococcus aureus-related septicemia; 1 had 2 episodes of Pseudomonas aeruginosa pneumonia; and 1 had bronchopneumonia) One patient in the rituximab group with serious infection (bronchopneumonia) subsequently died, although death may have been related to concomitant ischemic/vascular heart disease
Phase IIA extension Edwards, 2004 [52] Patients with RA MTX +/- rituximab, cyclophosphamide + rituximab 24 weeks 0/37 (0%) of patients who were treated with MTX developed serious infections. 1/38 (3%) of patients who were treated with rituximab (1000 mg) developed serious infections (1 case of gastroenteritis). 0/37 (0%) of patients who were treated with cyclophosphamide + rituximab (1000 mg) developed serious infections. 1/39 (3%) of patients who were treated with MTX + rituximab (1000 mg) developed serious infections (1 case of pyelonephritis) NR
REFLEX RCT (phase III) Cohen, 2006 [53] Patients with RA MTX +/- rituximab 24 weeks 79/209 (38%) of patients who were treated with MTX developed infections and 1/209 (3%) developed serious infections. 126/308 (41%) of patients who were treated with MTX + rituximab (1000 mg) developed infections and 7/308 (2%) developed serious infections. The overall infection rate (events/100 patient-years) was slightly higher in placebo-treated patients (154.6) than in rituximab-treated patients (138.2). The most common infections observed in both groups were upper respiratory tract infections, nasopharyngitis, urinary tract infections, bronchitis, and sinusitis. Rates of serious infections were 3.7/100 patient-years for placebo and 5.2/100 patient-years for rituximab; no statistical comparison of this difference was reported Of 7 serious infections that occurred in the rituximab-treated patients, 6 (1 case each of gastroenteritis, pyelonephritis, cat-bite infection, influenza, fever of unknown etiology, and de novo hepatitis B (HBV)) resolved without sequelae, while the other infection (gangrenous cellulitis) resulted in amputation of a toe
Open label trial Keystone, 2007 [54] Ongoing follow-up study of all patients enrolled in the three original clinical trials (2 phase II and 1 phase III) who had an incomplete response to or were intolerant of TNF inhibitors Rituximab vs. control group   No evidence to date for any increase in the incidence of infections and serious infections, with all patients having received at least 2 courses of rituximab. 25 Rates of infection (events/100 patient-years) were 83, 83, 80, and 88 for patients who had received 1, 2, 3, or 4 courses of rituximab, respectively; the corresponding rates for serious infections were 4.1, 4.6, 5.6, and 8.0 events/100 patient-years. Rates of infections and serious infections appear relatively stable with increasing courses of rituximab, however the extent of observation for patients receiving multiple courses of treatment is inevitably less than that for single-course treatment. Longer follow-up data is necessary. Irrespective of the number of courses of rituximab, serious infections occurred most often during the first 3 months after administration and declined thereafter. Overall, 68 of 1039 patients (7%) in the all-exposure population experienced a total of 78 serious infections following treatment with rituximab. The most common infections reported were upper respiratory tract infection, nasopharyngitis, urinary tract infection, bronchitis, and sinusitis. No incidences of opportunistic infections or tuberculosis were observed. The serious infection rate after course 1 (5.1 per 100 patient-years) remained stable through additional courses. The proportion of patients with circulating IgM and IgG levels below the LLN increased with subsequent courses; however, serious infection rates in these patients (5.6 per 100 patient-years in patients with low IgM levels and 4.8 per 100 patient-years in patients with low IgG levels) were comparable with those in patients with immunoglobulin levels above the LLN (4.7 per 100 patient-years) Three serious infections were fatal. Two occurred between course 1 and course 2; 1 patient had bronchopneumonia and a second patient had neutropenic sepsis following concomitant treatment with trimethoprim. The third infection-related fatality occurred after course 2, from septic shock in a 54-year-old female diabetic patient with a history of sepsis and recurrent urinary tract infections
Open label trial Furst, 2007 [24] Follow-up open label study on patients with RA Rituximab vs. control group   From a total of 1053 patients who had been exposed to at least 1 course of rituximab (total drug exposure of 2438 patient-years), 702 patients reported at least 1 infection, the most common being upper respiratory infections (32%) and urinary tract infections (11%). Rates of serious infections for patients who had received 1, 2, 3, or 4 courses of rituximab were 5.4, 4.6, 6.3, and 5.4 events/ 100 patient-years, respectively  
Open label trial Furst, 2008 [25] A 2-year follow- up of patients who participated in the phase IIA trial Rituximab, MTX, MTX + rituximab, cyclophosphamide + rituximab 2 year follow-up No significant differences in the rate of infections between the 4 treatment arms (MTX, rituximab, rituximab + cyclophosphamide, and rituximab + MTX)  
Open label trial Furst, 2010 [55] Patients from both phase II studies Rituximab vs. control group   Based on a total of 1669 patient-years of follow-up (145 patients had received at least 2 courses of rituximab), there was no evidence of an increase in the rate of infections compared with the data from the original phase II trials  

DANCER, Dose-ranging Assessment International Clinical Evaluation of Rituximab in RA trial; dcSSc; diffuse cutaneous systemic sclerosis; DMARD, disease-modifying antirheumatic drug; F/u, follow-up; HBV, hepatitis B virus; LLN, lower limit of normal; MTX, methotrexate; NR, not reported; RA, rheumatoid arthritis; RCT, randomized controlled trial; REFLEX, Randomized Evaluation of Long-Term Efficacy of Rituximab trial; SIE, serious infection event; TNF, tumor necrosis factor.

Rituximab is effective in patients with RA with an inadequate response to methotrexate, for whom conventional disease-modifying antirheumatic drugs (DMARDS) have failed or who have received one or more tumor necrosis factor (TNF) inhibitors.

The three pre-approval phase II and phase III RCTs conducted with rituximab in patients with RA reported low rates of infection, serious or not. 53 The rate of infection was higher with rituximab use in one RCT, 52 and slightly higher in placebo-treated patients in another study. 50 The incidence of serious infections was reported in one phase IIA RCT only: during a 48-week follow-up, six serious infections were reported in patients treated with rituximab regimens versus only one serious infection in a patient being treated with methotrexate alone; this difference was not statistically significant. 56

Further information on the risk of infections associated with rituximab therapy has emerged from open-label extensions to the RCTs. No significant difference in the rates of infection with the use of rituximab and no cases of tuberculosis (TB), opportunistic infections, or viral reactivations have been reported in the open-label RA extension studies to date ( Table 2 ).

A recent study suggested that there were no fatal or opportunistic infections prior to or after another biological DMARD (in patients with RA refractory to treatment) following rituximab treatment. 50 In a separate meta-analysis of the three rituximab clinical trials, the pooled odds ratios (OR) for serious infections at all doses of rituximab versus placebo did not reveal any statistically significant increased risk (OR 1.45, 95% CI 0.56–3.73). 54

Based on the results presented, treatment with rituximab for up to 3 years appears to be associated with a numerically increased incidence of infections (including serious infections). However no statistical difference regarding an increased risk for infection is evident and the risk appears lower than that associated with the TNF inhibitors. Long-term controlled data are necessary to allow a more precise definition of this risk. Thus, further studies are needed to elucidate the association of rituximab with infection in patients with RA, since current data do not indicate an increased risk of infections when using rituximab compared with concurrent control treatments.

5. Rituximab and infection in transplant patients

Rituximab off-label use includes organ transplantation. The use or rituximab has been increasing in the transplant population and an increasing number of infections have been reported. Few data are available concerning the risk of organ transplant recipients developing infections following rituximab therapy. Scemla et al. reported bacterial, viral, and fungal infection rates at 55.3%, 47.4%, and 13.2%, respectively, in kidney transplant patients who received rituximab therapy. 57 In kidney transplant patients who received rituximab therapy at two different doses (375 mg/m2/week four times or 1000 mg/m2/week two times), Tsapepas et al. reported a bacterial infection rate at 48% and 61.1%, respectively, a viral infection rate at 8.2% and 25.3%, respectively, and a fungal infection rate at 20% and 8.2%, respectively. 58 A recent retrospective study by Grim et al. observed no increased risk of infectious complications following rituximab therapy in renal transplant recipients. 59

Low-dose rituximab induction therapy in renal transplant recipients appears to have no influence on the incidence of cytomegalovirus (CMV) infection and CMV seroconversion. 60 However, because of the high incidence of CMV infection, especially for CMV-seronegative recipients who received rituximab, anti-CMV prophylaxis therapy needs to be considered. 60

In one study of 77 kidney transplant patients who received rituximab therapy, the incidence of bacterial infection was similar between these patients and another kidney transplant control group who did not receive rituximab, whereas the viral infection rate was significantly lower, and the rate of fungal infection was significantly higher in the rituximab group. 61 Nine out of 77 patients (11.68%) died after rituximab therapy, of which seven deaths (9.09%) were related to an infectious disease, compared to 1.55% in the controls (p = 0.0007). 61

An increased incidence of JC infection has also been described in transplant patients who receive rituximab. 61 Thus, after kidney transplantation, the use of rituximab is associated with a high risk of infectious disease and death related to infectious disease, and the independent predictive factors for infection-induced death were recipient age, bacterial and fungal infections, the combined use of rituximab, and anti-thymocyte globulin given for induction or anti-rejection therapy. 61

In conclusion, although few data are available regarding the association of rituximab with infection in organ transplant recipients, data from renal transplant patients suggest an increased risk of infection with the use of rituximab in this population.

6. Types of infection

Table 3 outlines the most important types of infection associated with rituximab use.5, 16, 19, 21, 30, 36, 41, 42, 44, 45, 49, 50, 53, 54, 59, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, and 122

Table 3 Cases in which addition of rituximab was likely associated with the development of infection

Infection No. of patients Pathogens (n) References
Bacterial infections      
Sinopulmonary infection ND Pneumonia (7), Staphylococcus aureus pneumonia (1), Streptococcus pneumoniae pneumonia (1), bronchitis (1), upper respiratory tract infections, nasopharyngitis, bronchitis, and sinusitis 30, 36, 50, 53, 54, 59, 62–64
Bacteremia ND Septic shock (3), bacteremia (5) 30, 36, 44, 54, 59, 64
Bacterial diarrhea ND Shigella (1) 50
Urinary tract infections ND No pathogens reported, pyelonephritis 53, 54, 59
Skin infections ND Erysipelas, gangrenous cellulitis 50, 53, 59
Bone and joint infections 2 Infection of right hip (1), septic polyarthritis with Ureaplasma urealyticum (1) 50, 65
Dental abscess 1   49
Listeriosis 1   81
Cat scratch disease 1   53
Mycobacterial infections      
Other non-tuberculous mycobacteria 4 Bacteremia caused by Mycobacterium wolinskyi (1), M. avium pleuritis (1), M. avium bacteremia (1), disseminated M. kansasii infection (1) 66, 67
Viral infections      
CMV disease 26 CMV esophagitis (1), pneumonia (6), and enterocolitis (4), disseminated CMV infection (1) 5, 19, 21, 59, 63, 68–71, 101
VZV 13   5, 41, 44, 45, 72–74, 101, 112
HSV 6 Disseminated HSV2 (1) 41, 63, 75
Hepatitis ND Not specified (3), de novo hepatitis B (2), HBV reactivation (21 cases in HBsAg-neg patients), HCV (2), HEV infection (1) 5, 44, 45, 53, 76–94, 107, 119, 120, 122
Gastroenteritis 4   50, 53, 95
Parvovirus 2   96, 97
Enterovirus 3 Enteroviral meningoencephalitis 98–100
Echovirus 1   112
JC virus 76 52 patients had lymphoproliferative disorders, two had SLE, one had rheumatoid arthritis (and oropharyngeal cancer that had been treated previously with chemotherapy and radiotherapy), one had idiopathic autoimmune pancytopenia, and one patient with NHL had a concomitant autoimmune hemolytic anemia 101–104
BK virus 1 BK virus CNS infection 105, 106
RSV 2   107, 108
West Nile virus 3   109–111
Influenza A virus 2   53, 112
Fungal infections      
Fungal infections (not specified)   Fungal pneumonia 30
Candida infections 4 esophagitis (1), candidemia (3) 30
Pneumocystis jiroveci (carinii) 13 Pneumonia 30, 42, 63, 113–116
Aspergillus spp 4 Aspergillosis 16, 117–119
arasitic infections      
Babesia microti 8 Babesiosis 121

CMV, cytomegalovirus; CNS, central nervous system; HBV, hepatitis B virus; HCV, hepatitis C virus; HEV, hepatitis E virus; HBsAg, hepatitis B surface antigen; HSV, herpes simplex virus; ND, not determined; NHL, non-Hodgkin lymphoma; RSV, respiratory syncytial virus; SLE, systematic lupus erythematosus; VZV, varicella zoster virus.

In a systematic review of the literature, Cornely et al. 123 analyzed 992 patients treated with either alemtuzumab, rituximab, or both; 409 patients (41.2%) were treated with alemtuzumab, 535 (53.9%) with rituximab, and 48 (4.9%) with both. The overall number of opportunistic infections (OI) diagnosed was 299 (30.1%). Etiologies were distributed as follows: 109 (36.5%) infections of unknown or unspecified origin, 100 (33.4%) viral reactivations, 44 (14.7%) bacterial infections, 26 (8.7%) fungal infections, 11 (3.7%) protozoal infections, and nine (3.0%) viral infections. Viral reactivations were most frequently due to CMV (n = 58, 19.4%), herpes simplex virus (HSV; n = 30, 10.0%), varicella zoster virus (VZV; n = 11, 3.7%), and Epstein–Barr virus (EBV; n = 1, 0.3%). Pneumonias accounted for 15.1% (n = 45) of observed bacterial infections, and included 11 Pneumocystis jiroveci pneumonia (PCP) cases (3.7%) and 37 (12.4%) blood stream infection cases. Death attributable to OI occurred in 20 patients (2%). Optional prophylaxis of viral infections was reported in eight articles (n = 404, 40.7%), and optional prophylaxis for PCP in nine articles (n = 435, 43.9%). 123

From our review of the literature a broad spectrum of infections has been associated with rituximab use in clinical trials, including respiratory tract infections (e.g., bronchopneumonia, nasopharyngitis, bronchitis, and sinusitis), 53 bacteremia, 53 sepsis,52 and 53 urinary tract infections (including pyelonephritis),52 and 53 gastroenteritis, 52 cellulitis, 53 septic arthritis, 53 cat-bite infection, 53 influenza,40 and 41 de novo hepatitis B (hepatitis B virus (HBV)), 41 herpes zoster, 40 HSV infection, 40 adenovirus infection, 40 systemic candidiasis, 56 and aspergillosis. 25 At the time of writing, we could find no published reports of TB in rituximab-treated patients in clinical trials.

Data from case reports, case series, and retrospective studies also correlate rituximab use with the development of a variety of bacterial, viral, fungal, and parasitic infections ( Table 3 ).

7. Bacterial infections

Representative bacterial infections attributed to rituximab use are shown in Table 3 . A small increase in serious bacterial infections in RA patients receiving rituximab l000 mg has been reported. 24 In addition, an increase in the rate of serious infections was seen in a cohort of 78 patients with RA who received a TNF-α blocking agent after rituximab treatment. 50 Thus, sinopulmonary infections are the most common bacterial infections that have been described in association with the use of rituximab, but further data from randomized controlled studies are needed to establish this association.

8. Mycobacterial infections

Several recent studies suggest that peripheral B cells are important in the host defense against mycobacteria.30, 66, and 67 Past history suggestive of TB was an exclusion criterion in the clinical trials of rituximab in RA, and in the vast majority of cases, study patients had previously received TNF inhibitors; nevertheless no reactivation of TB occurred. In NHL clinical trials where history of TB was not an exclusion criterion, no evidence of an increased incidence of TB was noted. 5 Infection with other mycobacteria has rarely been associated with rituximab. More specifically, bacteremia caused by Mycobacterium wolinskyi or Mycobacterium avium, M. avium pleuritis, and disseminated Mycobacterium kansasii infections have all been described.66 and 67 Since it is not clear whether rituximab or other immunosuppressants that were simultaneously administered promoted disease progression or caused mycobacterial disease, clinicians should remain vigilant for mycobacterial infections in patients selected for these therapies. Thus, there is an open issue regarding TB screening prior to rituximab initiation. The authors believe that such screening should be performed.

9. Viral infections

Data on the true incidence of viral infections after rituximab therapy are poor. Co-administration with other cytotoxic chemotherapeutic agents and the intensity and duration of T-cell-mediated immune suppression are significant cofactors increasing the infectious risk. 41 Humoral dysfunction related to rituximab therapy may cause loss of neutralization of free viral particles by specific antibodies and an increase in serious viral infections; this hypothesis needs further investigation.

Reactivation of chronic HBV infection is one of the most frequently reported serious viral infections.80, 82, 85, 86, 87, 88, 89, 107, and 120 In one RCT, opportunistic viral infections reported included three dermatomal herpes zoster infections and four localized herpes simplex infections. 5 Many isolated cases of other viral infections e.g. CMV, VZV, West Nile virus, influenza A, JC virus, BK virus, parvovirus, and enterovirus have been associated with rituximab use ( Table 3 ). 5

Upper respiratory tract viral infections were most frequently reported, however in most studies infection sites were not specified. In a review of 64 cases of severe viral infection after rituximab treatment, the most frequently experienced viral infections were HBV (39.1%, n = 25), CMV (23.4%, n = 15), VZV (9.4%, n = 6), and others (28.1%, n = 18). 5

In conclusion, it is still unclear whether rituximab adds to the risk of viral infection above that conferred by chemotherapy alone; this association has been studied mainly with particular viral infections including HBV, hepatitis C virus (HCV), herpes virus, and JC virus infection.

10. HBV reactivation

A recent review of the literature revealed that the most frequent viral infection complicating rituximab therapy for lymphoma was hepatitis B infection. HBV reactivation accounted for 39% of the reported cases, resulting in a high mortality of 52% due to hepatic failure.5, 77, and 124 There are increasing reports of HBV reactivation following rituximab therapy, either when used alone or in combination with chemotherapy. 125 While the addition of rituximab to CHOP chemotherapy may increase the risk of HBV reactivation, the precise magnitude of the increase is not clear with the available data.80, 82, 85, 86, 87, 88, 89, 107, and 120 The use of rituximab in hepatitis B surface antigen (HBsAg)-positive patients can be continued provided they receive a prophylactic antiviral for a prolonged duration (up to 6 months) after cessation of chemotherapy. 80

With the recent increase in rituximab use, HBV reactivation has been increasingly reported, even in patients who were thought to have cleared HBV ( Table 3 ).80 and 92 In a recent study of lymphoma patients with prior resolved hepatitis B, among HBsAg-negative/anti-hepatitis B core (HBc)-positive diffuse large B-cell lymphoma (DLBCL) patients treated with R-CHOP, 25% developed HBV reactivation. 122

In addition to the use of rituximab, other potential factors associated with HBV reactivation include the absence of anti-HBs and male sex.5, 77, and 124 In one report it was shown that R-CHOP therapy for lymphoma can increase the levels of serum HBV DNA and the risk of intrafamilial HBV infection when given to HBV carriers. 126 Therefore, HBV reactivation may occur in the setting of rituximab use, and close monitoring of HBV DNA and liver function testing during rituximab therapy for at least 6 months after the completion of administration is required, with an alternative approach of prophylactic antiviral therapy to prevent this potentially fatal condition.

11. HCV reactivation

Rituximab-related liver dysfunction has not been described in HCV-positive patients receiving rituximab combination chemotherapy. 127 Rituximab was reported to increase HCV viral load and alanine aminotransferase (ALT) levels in patients with HCV-related cryoglobulinemia (ALT was increased 10-fold and HCV viral load was increased 10-fold in one case) 128 and lymphoma (ALT was increased 25-fold in one case and HCV viral load was increased 5–10-fold in five cases). 129 Therefore, combined use of rituximab with chemotherapy poses an additional risk for exacerbation of HCV infection.

The influence of rituximab on HCV replication is not well understood. In one case, rituximab therapy for gastric cancer in a renal transplant recipient with chronic hepatitis C was complicated by cholestatic injury, an active hepatitis C replication with very high HCV RNA levels (increase of 1000-fold in HCV viral load after rituximab), and liver insufficiency. 129 In two patients who underwent ABO-incompatible renal transplantation and who received rituximab and had positive HCV RNA, cholestatic hepatitis C did not occur, but double-filtration plasmapheresis (DFPP) and cyclosporine failed to reduce hepatitis C viremia. 130 Another patient with refractory thrombotic thrombocytopenic purpura and membranoproliferative glomerulonephritis successfully treated with rituximab developed hepatitis C virus reactivation. 93 In another study of five HCV-infected patients with B-cell NHL undergoing treatment with rituximab-combination, all patients showed a significant increase in serum HCV RNA levels (at least 3-fold) with no occurrence of liver dysfunction. 131 Two of these patients received regimens without prednisone, suggesting that increased HCV viremia was associated not only with corticosteroid use, but also with anticancer agents or rituximab. 132 On the other hand, in one study, all seven patients who were HCV RNA-positive at the time of rituximab therapy for the treatment of transplant glomerulopathy, did not have significantly increased HCV RNA viremia or elevated levels of liver enzymes in the follow-up. 63

In another report, 35 HCV-positive patients with DLBCL received rituximab-containing combination regimens without any hepatotoxicity; considering the short follow-up period of their study such toxicity might have been missed. 132 In another study of 44 HCV-positive patients with DLBCL treated with CHOP/CHOP-like regimens +- rituximab, high viral load and evidence of active hepatitis or cirrhosis at liver biopsy was associated with more frequent hepatic failure under treatment and reduced survival. 132 Concomitant administration of R-CHOP plus anti-HCV treatment with pegylated interferon and ribavirin in four patients with HCV infection and DLBCL in the same study, resulted in excessive hematological toxicity. 132 On the other hand, sequential treatment with pegylated interferon plus ribavirin 3 months after chemotherapy in three patients was found effective, better tolerated, and resulted in a high rate of complete virus clearance.133 and 134

The lack of correlation between levels of HCV RNA and the extent of liver damage and variability of HCV RNA levels over time, limit strong conclusions regarding the association of rituximab with HCV infection and liver damage.128, 129, and 132 Kamar et al. found that rituximab therapy was not associated with a flare-up of chronic HCV infection in kidney transplant patients. 61 Finally, although HCV viral load can increase after rituximab treatment, 5 rituximab has been successfully used in HCV-associated cryoglobulinemia.5 and 128 This indicates that rituximab may be an effective treatment for immunologic manifestations of HCV infection.

In summary, the association of rituximab with HCV infection remains very complex since rituximab may exacerbate HCV infection, but in other cases it has been used for the treatment of HCV-related autoimmune phenomena. Physicians should monitor HCV viral load during rituximab therapy.

12. Herpes infection

Infections with herpes viruses such as CMV, VZV, and HSV have been described in association with rituximab use.5, 19, 21, 41, 44, 45, 59, 63, 68, 69, 70, 71, 72, 73, 74, 101, and 112 The most common herpes virus associated with rituximab is CMV and 26 cases have been described in the literature.5, 19, 21, 59, 63, 68, 69, 70, 71, and 101 In cases where CMV infection was specified, CMV enterocolitis, pneumonitis, and esophagitis were described ( Table 3 ).

EBV infection has not been associated with rituximab to date. In one case with disseminated EBV infection, rituximab was ineffective in treating central nervous system infection with EBV. 5 Other data suggest that EBV persists in cell populations not depleted by rituximab, such as EBV-infected oropharyngeal epithelial cells. 135 Finally, 13 cases of infection with VZV5, 41, 44, 45, 72, 73, 74, 101, and 112 and five cases of HSV41, 63, and 75 have been described in association with rituximab therapy ( Table 3 ). However, data from randomized controlled studies are needed to establish the association of rituximab use with the development of infections with herpes viruses.

13. Progressive multifocal leukoencephalopathy (PML)––JC virus

As of July 29, 2008, there were 76 reports in the manufacturer's global safety database of confirmed or suspected PML in patients receiving rituximab for any indication (69 in oncology indications, one autoimmune hemolytic anemia, five in other autoimmune disorders, and one in an unknown indication). 136 In one study rituximab was associated with a delay in the development of PML in HIV-negative patients with lymphoproliferative disorders treated with rituximab compared to patients treated with similar chemotherapeutic regimens without rituximab. 137 According to a report by the FDA, a total of 23 cases of PML have been documented in patients on rituximab for hematological malignancies mostly in combination with chemotherapy or stem cell transplantation. 1

Carson et al. reported 57 rituximab-associated PML cases in HIV-negative patients. Median time from last rituximab dose to PML diagnosis was 5.5 months (range 0.3–66.0) and the overall incidence of fatality was 90%. 104 Kamar et al. showed that the incidence of JC viremia in rituximab-treated solid-organ transplant patients was 5.5%. 61 The exact role of rituximab in the development of PML is unclear, as humoral immunity is thought to be of little importance in the latency of JC virus, although the loss of the B-cell antigen presenting cell function may be critical. The effect of rituximab on T-lymphocyte function as a potential mechanism of JC virus reactivation remains an area of active inquiry. 138 Thus, the causal relationship between PML and rituximab remains unclear.

14. Fungal infections

Humoral immune deficiencies increase the risk for opportunistic fungal infection, and a reduction in antigen-specific cellular immunity impairs host protection against fungi. A recent study demonstrated that the addition of rituximab to CHOP increased the risk of fungal infection in a very elderly population. 30 Pneumocystis jiroveci (previously known as Pneumocystis carinii) pneumonia (PCP) may occur in a variety of hematological diseases. 115

Although PCP has not been reported in the rituximab treatment arm of large RCTs, based on data from small trials, retrospective studies, and case reports, 13 cases of PCP have been described in the literature in association with rituximab use in patients with hematological malignancies.30, 42, 63, 113, 114, 115, and 116 Although these patients were also receiving other immunosuppressive medications, the strong temporal relationship between the rituximab infusions and the onset of the disease suggests that rituximab played a decisive role in the development of the opportunistic infection. Another study showed that the addition of rituximab to CHOP-like regimens, such as CHOP and CHOP-14, with or without etoposide, increased the incidence of PCP (13% in the rituximab arm vs. 4% in the other arm). 30 No cases of PCP have been reported in patients with autoimmune disorders receiving rituximab as treatment.

Four case reports have been published that describe the occurrence of aspergillosis; one in a patient with autoimmune thrombocytopenic purpura and two in patients with post-transplant lymphoproliferative disorders that were treated with rituximab. 139 Four cases of Candida infection have also been described in association with use of rituximab.16, 117, 118, and 119 As all these patients received extensive additional immunosuppressive treatment, the exact role of rituximab is difficult to define. However, experiments in B-cell deficient mice are in line with a mild impairment in antifungal immunity. 139

The possibly increased susceptibility to P. jiroveci and fungal infection with the use of rituximab may suggest the need to administer prophylactic treatment with antifungals and/or trimethoprim–sulfamethoxazole during R-CHOP therapy. Due to the high incidence of Aspergillus and Candida infection, it may be more appropriate to use itraconazole or posaconazole rather than fluconazole as primary prophylaxis in these patients. 140

15. Parasitic infections

Parasitic infections have rarely been described in association with rituximab use, although eight cases of babesiosis were described in one study. The authors concluded that rituximab effects on naive B cells that are responsible for antibody production in response to a new babesial infection could be involved. 121 More data are needed to elucidate the possible association of infliximab use with parasitic infections.

16. Immunization effects

The response to vaccination after rituximab could be reduced since rituximab causes B-cell depletion; 141 it is recommended that any vaccinations should be given before initiating treatment. A single study found that humoral responses to influenza vaccination were lower among patients treated with rituximab compared to RA patients who had received non-biological DMARDs and healthy controls. 142 Data from a recent RCT suggest that patients with RA treated with rituximab can be effectively and safely vaccinated, but to maximize response, polysaccharide and primary immunizations should be administered prior to rituximab infusions. 143 A recent clinical trial showed that rituximab reduces humoral responses following influenza vaccination in RA patients, with a modestly restored response 6–10 months after rituximab administration. 143 Recent studies suggest that anti-tetanus immune responses are decreased shortly after rituximab treatment, while immune responses to neoantigens and polysaccharides, which are B-cell-dependent, are decreased following rituximab treatment. 142

Despite the suboptimal response, appropriate vaccination (such as against influenza or pneumococcus) should be administered when indicated.142 and 143 Due to the paucity of data on the use of live attenuated vaccines while on rituximab, such vaccines should preferably be administered prior to rituximab use.

17. Limitations

We identified certain limitations in the studies that have examined the association of rituximab with infection. Firstly, the true infection rates may be higher than those reported in clinical trials since minor infections (grade 1 and grade 2) are possibly overlooked both by the patients and the doctors, and are under-reported. In certain reports (mostly case reports) authors did not provide adequate data regarding the strength of association of rituximab with infection and thus we could not independently analyze the strength of evidence regarding this association in these cases. Furthermore, variances in reporting rates of neutropenia, immunoglobulin levels, infections as adverse events by the doctors, and the heterogeneity of the trials, the different patient selection criteria, and the different extent of bone marrow involvement by different subtypes of lymphomas may account for the differences in infection rates in clinical trials.

18. Conclusions

In conclusion, recent data show that rituximab maintenance therapy significantly increases the risk of both infection and neutropenia in patients with lymphoma or other hematological malignancies. Novel prophylaxis and/or pre-emptive treatment strategies should be tailored for these patients when treated with rituximab. On the other hand, data available to date do not indicate an increased risk of infection when using rituximab compared with concurrent control treatments in RA. However, there is a lack of sufficient long-term data to allow such a statement to be definitively made and caution regarding infections should continue to be exercised, especially in patients who have received repeated courses of rituximab, are receiving other immunosuppressants concurrently, and in those whose immunoglobulin levels have fallen below the normal range. Further studies are needed to clarify the association of rituximab with infection. Education of physicians and patients about the association of rituximab with infectious complications, monitoring of absolute neutrophil count and immunoglobulin levels, identification of high-risk groups for the development of infectious complications, and timely vaccination of these groups are clearly needed.

Conflict of interest statement

The authors have no conflict of interest to declare.

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Footnotes

a Department of Medicine, Division of Infectious Diseases, David Geffen School of Medicine at UCLA, 10833 Le Conte Ave., CHS 37-121, Los Angeles, CA 90095, USA

b First Department of Propedeutic Medicine, Laikon University Hospital, University of Athens Medical School, Athens, Greece

c Department of Internal Medicine, University Hospital, Medical School, University of Crete, Heraklion, Greece

d Fourth Department of Internal Medicine, Attikon University Hospital, University of Athens Medical School, Athens, Greece

lowast Corresponding author. Tel.: ++1 310 825 7225; fax: ++1 310 2080140.

Corresponding Editor: William Cameron, Ottawa, Canada.