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Refined Medullary Blast and White Blood Cell Count Based Classification of Chronic Myelomonocytic Leukemias

Leukemia Research

Highlights

 

  • we showed that proliferative CMML types do worse as compared to dysplastic types.
  • progression rates of CMML with <5% blasts are lower as compared to CMML I + II.
  • erythroid insufficiency of all CMML types is not as severe as in RCMD, RAEB I and II.
  • separate CMML with less than 5% medullary blast count from CMML I.

Summary

Since 2001, chronic myelomonocytic leukemia (CMML) is classified by the WHO as myeloproliferative/myelodysplastic neoplasm. Herein we tried to better describe CMML patients with regard to hematological characteristics and prognosis using data of the Duesseldorf registry. We created 6 CMML subgroups, by dividing dysplastic and proliferative CMML at the cut-off of white blood cell count of 13,000/μl and splitting these two groups into 3 subgroups: CMML 0 with <5% blasts (n = 101), CMML I with 5%-9% blasts (n = 204) and CMML II with 10%-19% blasts (n = 81). For comparison we included patients with RCMD, RAEB I and II. The newly created CMML 0 group had better prognosis than CMML I and II, median survival times were 31 months (ms), 19 ms and 13 ms, respectively (p < 0.001). Median survival times between the corresponding dysplastic and proliferative subgroups 0 and 1 differed significantly: CMML 0 dysplastic 48 ms and CMML 0 proliferative 17 ms (p = 0.03), CMML I dysplastic 29 ms and CMML I proliferative 15 ms (p = 0.008), CMML II dysplastic 17 ms and CMML II proliferative 10 ms (p = 0.09). Outcome of CMML patients worsens with increasing medullary blasts and when presenting as proliferative type. Therefore it is justified to separate CMML with <5% medullary blasts.

Keywords: CMML, MDS, MDS/MPN, Overlap, Prognosis, CPSS.

1. Introduction

Since 2001 chronic myelomonocytic leukemias (CMML) are classified as mixed myeloproliferative/myelodysplastic neoplasms. Other entities in this group are BCR/ABL negative chronic myeloid leukemia, juvenile myelomonocytic leukemia and finally myeloproliferative/myelodysplastic neoplasms, unclassified [1] . The revised version of the WHO classification in 2008 still classifies the CMML as an overlap syndrome. During the validity of the French-American-Britain (FAB) leukemia cooperative Group classification starting in 1982 the CMML was considered as myelodysplastic syndrome [2] . The FAB group stated that CMML usually presents with medullary blast counts fewer than 5%. In 1994 the FAB group proposed to split CMML into a dysplastic subtype with a white blood cell count (WBC) less than 13000/μl and a proliferative type with WBC of more than 13000/μl [3] (summary of diagnostic criteria see Table 1 ). Cytogenetic abnormalities are present in 20-40% of patients[4] and [5], there have been efforts on creating cytogenetic risk categories [6] . Frequently molecular alterations are found in CMML as well, which however are not specific for this entity. Mutations of ASXL1, TET2, SRSF2, RUNX1, NRAS, CBL are frequently found in CMML[7], [8], and [9]. Some of them are associated with prognostic relevance, i.e. ASXL1 [10] and TET2 [11] Prognostic scores have been developed for CMML[12], [13], [14], and [15],lately the CMML prognostic scoring system (CPSS), which consists of WHO-subtype, FAB-subtype, CMML specific cytogenetic risk classification and red blood cell transfusion dependency [16] . The Duesseldorf-Score which was already established in 1992 consists of the following parameters: bone marrow blasts greater than or equal to 5%, LDH greater than 200 U/I (upper normal range), hemoglobin less than or equal to 9 g/dl, and platelets less than or equal to 100.000/μI. As a function of their total score, patients were divided into three risk groups [13] Since the classification of CMML as MPN/MDS, CMML is often excluded from clinical trials. To draw attention back to CMML we tried to better describe patients with regard to their relationship to MDS and MPN.

Table 1 Diagnostic criteria for CMML at different time points.

WHO 2008 FAB 1982 FAB 1998
Classified as MDS/MPD Classified as MDS Classified as
    MDS-CMML<13×109/l
    MPD-CMML>13×109/l
blood monocytosis >1×109/l blood monocytosis >1×109/l blood monocytosis >1×109/l
CMMLI<10% blasts in BM < 20% blasts in BM, < 5% < 20% blasts in BM,
CMMLII10% -19% blasts in BM, 5% -19% blasts in PB, or blasts in PB < 5% blasts in PB
auer rods present irrespective of blast count    
No Philadelphia chromosome or    
BCR/Abl fusion gene    
No rearrangement of PDGFA or PDGFB    
Dysplasia in one or more myeloid lineages. If    
myelodysplasia is absent or minimal, the diagnosis of CMML    
may still be made if the other requirements are met and    
an acquired, clonol cytogenetic or molecular genetic    
abnormality is present    
monocytosis has persisted for at least 3 month    
all other causes of monocytosis have been excluded    

BM=bone marrow, PB= peripheral blood

2. Methods

Our retrospective study included 2507 patients from the Duesseldorf MDS registry, diagnosed between 1975 and 2012, who received best supportive care or disease specific therapy except for allogeneic transplantation. The diagnostic procedures were the same as reported earlier[17] and [18]. Diagnoses were made according to the proposals of the WHO 2008 classification [1] . Cytogenetic analyses at the time of diagnosis were performed at the Institute of Human Genetics, Heinrich-Heine University, Duesseldorf. The clinical data were gathered from the original patients’ charts. Follow-up data were obtained from our outpatient department or by contacting the primary care physician. Local ethics approval for this study and informed consent were obtained. Patients were censored at the date of last follow-up. Overall survival was calculated using the Kaplan-Meier method, to compare the parameter LDH, hemoglobin etc. the Mann-Whitney-U test was used.

3. Results

We included 386 patients with CMML into our analysis. In a first step, we reanalyzed the prognostic meaning of medullary blast count in CMML and found that not only a separation of CMML I from CMML II using the 10% blast cut-off, but also a separation using a blast cut-off of 5% is of importance. Patients with less than 5% of medullary blast count had a better survival time than CMML I and CMML II patients, corresponding median survival times were 31 months (ms), 19 ms and 13 ms, respectively (p < 0.0001) ( figure 1 ). As a consequence, we newly defined a group of CMML patients with less than 5% blast, called CMML 0.

gr1

Figure 1 Kaplan-Meier curve of survival of CMML 0 versus CMML I versus CMML II.

Then we analyzed, if dysplastic and proliferative CMML types at the cut-off of a white blood cell count of 13,000/μl differ with regard to hematological characteristics and prognosis. According to the above mentioned grouping system we identified 204 dysplastic CMML patients, subdivided into 61 dysplastic CMML 0-, 105 dysplastic CMML I- and 38 dysplastic CMML II-patients and further 182 proliferative CMML patients subdivided into 40 proliferative CMML 0-, 99 proliferative CMML I- and 43 proliferative CMML II-patients. Obviously, all CMML types were equally distributed when comparing dysplastic and proliferative types. For comparison with patients with MDS we included 1293 RCMD patients, 387 RAEB I patients and 441 RAEB II patients. Patients’ characteristics are summarized in Table 2 .

Table 2 Patients characteristics.

  n m in % f in% age median and range median survival time in month median and range WBC/μl median and range Hemoglobin g/dl median and range platelet count/μl median and range LDH U/l median and range monocyte count/μl karyotype risk group according to CPSS(%) CPSS risk groups (%) Duesseldorf Score risk groups (%) Cumulative risk of AM L after 2 years %
CMML0 101 65 35 73 [48-90] 31 10300[200-138000] 10.9 [4.8-15.9] 143 [8-978] 210 [103-1435] 2275 [1000-16370] 66 24 10 40 23 36 0 23 73 4 7
CMML0dysplastic 61 67 33 73[52-88] 48 6400 [2000-12100] 10.8 [5.6-15.9] 139 [8-863] 208 [103-1200] 1587 [1000-4708] 75 17 8 66 22 11 0 26 70 4 4
CMML0 proliferative 40 60 40 74 [48-90] 17 20650 [13400-138000] 11.6 [4.8-15.3] 145 [21-978] 242 [152-1435] 3815 [1098-16370] 53 35 12 0 25 75 0 19 78 3 12
CMMLI 204 64 36 73 [30-96] 19 12150 [1500-147800] 10.7 [2.5-16.3] 104 [1-979] 219 [75-1176] 2484 [1000-44340] 67 19 14 30 32 32 5 0 62 38 18
CMMLI dysplastic 105 65 35 72 [43-96] 29 6100 [1500-12600] 10.5 [4.7-16.3] 99 [6-744] 200 [95-1176] 1365 [1000-12600] 71 19 10 60 18 22 0 0 64 36 13
CMMLI proliferative 99 63 37 73 [30-91] 15 25600 [13000-147800] 10.8 [2.5-15.5] 112 [1-979] 242 [75-796] 5480 [1000-44340] 62 19 19 0 50 38 12 0 60 40 21
CMML II 81 63 37 71 [32-91] 13 15300 [2700-145000] 9.9 [3.9-15.7] 84 [2-1069] 238 [98-1350] 3119 [1000-88450] 65 21 14 0 10 90 0 0 44 56 36
CMML II dysplastic 38 58 42 69 [32-88] 17 6100 [2700-12600] 10.3 [4.7-15.7] 89 [2-1069] 199 [98-1350] 1640 [1000-7378] 64 22 14 0 18 82 0 0 58 42 35
CMML II proliferative 43 67 33 74 [44-91] 10 30100 [13800-145000] 9.7 [3.9-15.1] 80 [3-907] 262 [144-904] 8161 [1896-88450] 67 20 13 0 0 75 25 0 32 68 37
RCMD 1293 57 43 72 [19-94] 34 3900 [4-46000] 9.4 [2.2-16.9] 132 [1-1540] 195 [2-2500] 200 [0-4774]                     10
RAEBI 387 58 42 70 [24-105] 18 3200 [4-57600] 9.3 [2.6-17.5] 94 [0-1408] 208 [0-3800] 151 [0-5640]                     24
RAEBII 441 58 42 71 [18-93] 11 2800 [4-139000] 9.1 [3.4-15.9] 80 [3-809] 222 [0-4680] 99 [0-4488]                     44

WBC= white blood cell count, LDH= laktatdehydrogenase, CPSS=CMML Prognostic Scorring System, m=male, f=female, n= number of patients

3.1. Hematological features

CMML 0 patients had significant higher hemoglobin (Hb)-levels in comparison to RCMD patients (10.9 g/dl vs 9.4 g/dl, p < 0.001), CMML I patients had higher Hb-levels in comparison to their dysplastic counterpart RAEB I as well (10.7 g/dl vs 9.3 g/dl), as had CMML II (Hb 9.9 g/dl vs. 9.1 g/dl). Median platelet counts did not differ. Between the corresponding dysplastic and proliferative CMML subtypes hemoglobin levels and platelet counts did not differ. LDH levels were significantly higher in CMML I and II proliferative than in the CMML I and II dysplastic (p < 0.0001) (see Table 2 ). In CMML 0 the difference did not reach the significance level (p = 0.067).

3.2. CPSS

The CPSS was available for 107 CMML patients. The patients were assigned to four risk groups low, intermediate I, intermediate II and high risk, median survival times were as follows: 63ms, 36ms, 15ms and 16ms (p = 0.024). 29 patients were in the low risk group, 12 CMML 0 dysplastic- and 17 CMML I dysplastic- patients, 27 patients were in the intermediate I group, 4 CMML 0 dysplastic-, 3 CMML 0 proliferative-, 5 CMML I dysplastic-, 13 CMML I proliferative-, 2 CMML II dysplastic–patients, 45 patients were in the intermediate II group 2 CMML 0 dysplastic-, 9 CMML 0 proliferative-, 6 CMML I dysplastic-, 10 CMML I proliferative-, 9 CMML II dysplastic- and 9 CMML II proliferative and 6 patients were in the high risk group 3 CMML I proliferative- and 3 CMML II proliferative patients.

Concerning the cytogenetics 88 patients were assigned into the low risk cytogenetic category, as defined by Such et al. [16] 27 CMML 0, 42 CMML I, and 19 CMML II patients, 28 patients were assigned into intermediate risk cytogenetic category 10 CMML 0, 12 CMML I,and 6 CMML II patients, 17 patients had high risk cytogenetic findings 4 CMML 0, 9 CMML I,and 4 CMML II patients.

3.3. Duesseldorf score

According to the Duesseldorf Score CMML patients are assigned to 3 risk groups low intermediate and high risk; median survival times were: 87ms (19 patients, 13 CMML 0 dysplastic- and 6 CMML 0 proliferative- patients) vs. 28ms (200 patients, 35 CMML 0 dysplastic-, 25 CMML 0 proliferative-, 56 CMML I dysplastic-, 53 CMML I proliferative-, 19 CMML II dysplastic- and 12 CMML II proliferative- patients) vs 11 ms (110 patients, 2 CMML 0 dysplastic-, 1 CMML 0 proliferative-, 32 CMML I dysplastic-, 35 CMML I proliferative-, 14 CMML II dysplastic- and 26 CMML II proliferative- patients) (p < 0.001).

3.4. Median survival

First we compared the median survival times between the newly created subgroups of CMML, CMML 0, I and II which differed significantly from each other (31 ms, 19 ms, 13 ms respectively) (p < 0.0001) (see figure 1 ).

Median survival times between the corresponding dysplastic and proliferative subgroups with the same blast counts differed: CMML 0 dysplastic 48 ms and CMML 0 proliferative 17 ms (p = 0.03), CMML I dysplastic 29 ms and CMML I proliferative 15 ms (p = 0.008) and CMML II dysplastic 17 ms and CMML II proliferative 10 ms (p = 0.09) (seeFigure 2, Figure 3, and Figure 4).

gr2

Figure 2 Kaplan-Meier curve of survival of CMML 0 dysplastic vs CMML 0 proliferative.

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Figure 3 Kaplan-Meier curve of survival of CMML I dysplastic vs CMML I proliferative.

gr4

Figure 4 Kaplan-Meier curve of survival of CMML II dysplastic vs CMML II proliferative.

In the next step we compared the median survival times of the CMML subtypes with their dysplastic MDS counterparts. There was no difference between the corresponding pairs in median survival times in the dysplastic types: CMML 0 48 ms and RCMD 34 ms and CMML II 19 ms and RAEB II 18 ms (p values n.s). The dysplastic CMML I patients had significantly longer median survival time of 29 ms in comparison to RAEB I 18 ms (p= 0.004). CMML 0 proliferative had a worse survival than RCMD (17 vs 34 ms, p = 0.01). The median survival times between CMML I proliferative and RAEB I and CMML II proliferative and RAEB II did not differ (15 ms vs 18 ms and 10 ms vs 11ms, respectively).

3.5. AML evolution

AML rates at 2 years after diagnosis differed between CMML 0, I and II with 7%, 18% and 36% of patients, respectively (p < 0.0001) (see figure 5 ). AML rates between the corresponding dysplastic and proliferative subgroups did not differ as well as corresponding dysplastic CMML and MDS subgroups (see Table 2 ).

gr5

Figure 5 Kaplan-Meier curves of cumulative AML evolution of CMML 0, I and II.

4. Discussion

Based on data of 386 patients with CMML we were the first, who could show that in parallel to the myelodysplastic syndromes a group of patients with CMML and less than 5% blasts in the bone marrow has a higher median survival than those with 5 to 9% blasts. Besides, we showed that proliferative CMML types do worse as compared to dysplastic types, even after separating 3 CMML groups according to their medullary blast counts. Progression rates of the CMML with less than 5% medullary blast count are significantly lower as compared to CMML I as well as CMML II types. In addition we could show that erythroid hematopoietic insufficiency of all CMML types is not as severe as in RCMD, RAEB I, and RAEB II. Such et al. utilized the prognostic impact of proliferation and increased medullary blast counts, together with cytogenetic categories and hematopoietic insufficiency ending up in 4 different risk groups that nicely identifies patients with different prognosis [16] . We also showed that the Duesseldorf Score works well in CMML and we were able to validate the Duesseldorf score for CMML 0 as well. The group of CMML 0 patients with an available CPSS was too small to be significantly different according to CPSS-risk groups. This should be validated with a larger and independent data set.

These results fit into the theory of a correlation of hematopoietic insufficiency and proportion of a malignant cell clone in the marrow, which is well described in the myelodysplastic syndromes - with increasing medullary blast count the risk of progression rises and median survival drops. Up to now, no study addressed this topic in detail, as most reports only separated patients with 5-9% versus 10-19% [19] [18] . Based on our results, it is justified to separate a CMML “0” presenting with less than 5% medullary blasts, as this group, both in its dysplastic as well as in its proliferative shape has a better prognosis and a lower risk of progression to AML than CMML I and II.

Initially, our intention was to analyze if dysplastic CMML types could be reclassified within the MDS types, i.e. RCMD, RAEB I and RAEB II. However, we could show that with regard to hematopoietic characteristics as well as cytogenetic features, dysplastic CMML is closer to proliferative CMML as to RCMD, RAEB I, and RAEB II. Erythroid hematopoietic insufficiency is less severe in CMML, and cytogenetic aberrations are less frequent in CMML as compared to MDS types. That is properly why CMML I in our cohort has a longer median survival time than RAEB I, median hemoglobin levels are 9.3 g/dl in RAEB I and 10.5 g/dl in CMML I, further 21% of RAEB I patients have high or very high risk cytogenetics according to IPSS-R whereas only 10% of CMML I have high risk cytogenetics according to CPSS.

Earlier critics on the WHO-classification of CMML should be extenuated.

5. Conclusion

In summary, we propose to separate CMML with less than 5% medullary blast count from the CMML I group and to separate dysplastic from proliferative types within CMML 0, CMML I, and CMML II. This refined categorization potentially has impact on treatment decision making.

Acknowledgement

Schuler E. analysed the data and wrote the paper, Schroeder M. performed the research, Neukirchen J. contributed essential data, Strupp C. contributed essential data, Xicoy B. analysed the data, Kündgen A. analysed the data, Hildebrandt B. contributed essential data, Haas R, analysed the data, Gattermann N. designed the research study and analysed the data, Germing U designed the research study, analysed the data and wrote the paper.

The authors state that they have no conflicts of interest.

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Footnotes

a Department of Hematology, Oncology and Clinical Immunology, Heinrich-Heine-University, Düsseldorf, Germany

b Department of Human Genetics and Anthropology, Heinrich-Heine-University, Düsseldorf, Germany

lowast Corresponding author. Department of Hematology, Oncology and Clinical Immunology Heinrich-Heine-University Moorenstr. 5 40225 Düsseldorf, Germany Tel.: +49 211 8117720 fax: +49 211 8118853.