Dysplastic erythroid precursors in the myelodysplastic syndromes and the acute myeloid leukemias: Is there biologic significance? (How should blasts be counted?)

Additional prognostic impact of the percentage of erythroid cells in the bone marrow of patients with myelodysplastic syndromes

In patients with myelodysplastic syndromes (MDS) the impact of the percentage of erythroid precursors in the bone marrow has been the subject of considerable debate, especially with regard to prognosis. We examined the prognostic impact of the percentage of erythroid cells in the bone marrow (bmery) in 2453 primary untreated MDS patients in a retrospective multi-center analysis. Bmery were quantified in bone marrow smears at the time of diagnosis and were correlated with overall survival (OS) and AML evolution. We identified three distinct risk categories: "< = 10% bmery" (poor), "11-25 or >45% bmery" (intermediate), and "26-45% bmery" (good) with distinct OS of 23, 40 and 48 months, respectively. The percentage of bmery showed prognostic significance concerning OS (Dxy = 0.08, p < 0.001) and AML-free survival (Dxy = 0.15, p < 0.001). Considering the IPSS-R by stratification, the Dxy were 0.09 for survival, and 0.18 for transformation (p < 0.001). Added to the IPSS-R, bmery enhances the prognostic power for both survival (Dxy = 0.39) and time to AML (Dxy = 0.59). Survival and time to AML differ in MDS according to the percentage of bmery. The best outcome was found in those who had normal or near normal bmery counts. Moreover, adding bmery as differentiating feature to the IPSS-R may enhance its prognostic significance.

Comparison of blast percentage calculated based on bone marrow all nucleated cells and non-erythroid cells in myelodysplastic syndromes with erythroid hyperplasia

It is controversial whether blast percentage based on all nucleated cells (ANC) or non-erythroid cells (NEC) more accurately reflects the prognosis of patients with myelodysplastic syndromes (MDS). We considered that the impact of blast percentage on survival should be similar in MDS with erythroid hyperplasia (MDS-E) and MDS with no erythroid hyperplasia (MDS-NE), and from this perspective, we retrospectively analyzed 322 patients, including 44 with MDS-E and 278 with MDS-NE. Overall survival was similar between the MDS-E and MDS-NE groups (P = 0.94). In a subgroup of patients with bone marrow (BM) blasts of < 5%, no difference in survival was found between MDS-E and MDS-NE by either calculation method. However, in patients with a blast percentage between 5 and 10%, a significant difference in survival was observed only when the blast percentage in MDS-E was calculated from ANC (P < 0.001 by ANC and P = 0.66 by NEC). A similar result was observed when we analyzed the remaining patients with higher blasts together with those with blasts between 5 and 10%. These results suggest that the calculation of the BM blast percentage based on NEC in MDS-E provides a blast percentage value with a clinical impact consistent with that in MDS-NE.

The challenging task of enumerating blasts in the bone marrow

Enumeration of blasts in the bone marrow is critical for diagnostic, prognostic, and therapeutic response evaluation in myelodysplastic syndromes, myeloproliferative neoplasms and acute leukemias. However, few studies have examined the accuracy and precision of marrow blast counting using standard microscopic procedures. In our study, 4 experienced hematopathologists evaluated blast percentages in marrow using either differential counts on aspirate smears or visual estimates on CD34-stained trephine biopsies. Results of an independent observer's manual counts of individual labeled and unlabeled cells performed on high resolution digital images of CD34-stained trephine biopsies were designated as the "Digital Reference." Hematopathologists' blast counts showed excellent interobserver reproducibility, but the counts in smears and trephine biopsies correlated poorly with each other. Compared to the Digital Reference, both smear and trephine evaluations showed positive bias and high variability. The biopsy showed less variability but higher positive bias relative to the smears, indicating that counts were overestimated more in the hematopathologists' biopsy evaluation. Flow cytometric counts correlated well with the Digital Reference, and cases with high blast count generally showed worse cytogenetic findings. Our results demonstrate the need for better counting methods if significant decisions are made based on microscopic enumeration of blasts. Further efforts should be made to develop markers to better define blast cells and perhaps incorporate automated digital imaging technologies to enumerate them. Also, consideration should be given to quantifying blasts per marrow area in biopsies instead of per nucleated cells.

Diagnostic algorithm for lower-risk myelodysplastic syndromes

Rapid advances over the past decade have uncovered the heterogeneous genomic and immunologic landscape of myelodysplastic syndromes (MDS). This has led to notable improvements in the accuracy and timing of diagnosis and prognostication of MDS, as well as the identification of possible novel targets for therapeutic intervention. For the practicing clinician, however, this increase in genomic, epigenomic, and immunologic knowledge needs consideration in a "real-world" context to aid diagnostic specificity. Although the 2016 revision to the World Health Organization classification for MDS is comprehensive and timely, certain limitations still exist for day-to-day clinical practice. In this review, we describe an up-to-date diagnostic approach to patients with suspected lower-risk MDS, including hypoplastic MDS, and demonstrate the requirement for an "integrated" diagnostic approach. Moreover, in the era of rapid access to massive parallel sequencing platforms for mutational screening, we suggest which patients should undergo such analyses, when such screening should be performed, and how those data should be interpreted. This is particularly relevant given the recent findings describing age-related clonal hematopoiesis.

Diagnostics and Prognostication of Myelodysplastic Syndromes

MDS are a heterogeneous and complex group of clonal hematological neoplasms arising from a hematopoietic stem cell, and characterized by ineffective hematopoiesis, resulting in increased apoptosis in the bone marrow and peripheral cytopenia, which involves one or more lineages. Epigenetic changes are reported as ‘founder’ mutations in the case of MDS. Its incidence in the general population has been reported as five new MDS diagnoses per 100,000 people. It affects men more frequently than it does women, and its incidence increases with age. The diagnostic classification, now in use, is the one of the World Health Organization, revised in August 2016. It recognizes six distinct entities in addition to a provisional entity of childhood. In most of the cases, diagnosis is based on the morphologic quantitative and qualitative evaluation of the peripheral blood and bone marrow using basic hematological techniques. Bone marrow biopsy and flow cytometric immunophenotyping also offer support for further diagnostic elucidation, while cytogenetics and molecular genetics are presently fully integrated into prognostication, treatment processes, and decision-making.

Revisiting erythroleukemia

PURPOSE OF REVIEW

The 2016 WHO classification of hematopoietic and lymphoid neoplasms alters the diagnostic criteria for erythroleukemia, including eliminating the erythroid/myeloid type of acute erythroleukemia, which was a prior subcategory of acute myeloid leukemia, not otherwise specified. Only pure erythroid leukemia remains in the WHO classification. This review will summarize the literature that contributed to that classification change as well as recent literature on the significance of the change.

RECENT FINDINGS

There is now a large body of literature on the negative prognostic impact of erythroid predominance, defined as 50% or more bone marrow erythroid cells, in myelodysplastic syndromes (MDSs). Recent studies have found similarities between erythroleukemia, especially the erythroid/myeloid type, and the erythroid-rich MDS cases. On the basis of these data, the WHO now reclassifies cases of the prior erythroid/myeloid acute erythroleukemia group based on the total blast cell count. This change moves such cases into an MDS category, usually MDS with excess blasts. This approach, however, may cloud the significance of erythroid predominance in this group of patients.

SUMMARY

The report clarifies the current criteria for a diagnosis of erythroleukemia as well as the ongoing challenges in classifying this group of erythroid rich bone marrow disorders.

Re-evaluation of acute erythroid leukemia according to the 2016 WHO classification

In the recent update of WHO classification, the definition of myeloid neoplasms with erythroid predominance has been modified shifting the main criteria for calculating blast percentage from non-erythroid cells (NEC) to all nucleated marrow cells (ANC). Thus, the cases previously classified as erythroid/myeloid subtype of acute erythroid leukemia (AEL) based on the 2008 WHO will now be categorized either as myelodysplastic syndrome with excess blasts (MDS-EB) or acute myeloid leukemia, not otherwise specified (AML-NOS). However, the clinical significance of this new classification has not been demonstrated. Thus, we reviewed a leukemia database and reclassified 38 cases previously diagnosed as AEL, erythroid/myeloid subtype, with the consideration of 2016 revision criteria. Twenty seven (71%) of them had >20% blasts in NEC but less than 20% blasts in ANC, and 11 (29%) had >20% in both NEC and ANC. There was no significant difference in overall survivals (OS) among AEL, MDS-EB, and AML-NOS (non-erythroid predominance, NEP). However, AML with myelodysplasia-related changes showed significant shorter OS than AEL, MDS-EB and AML-NOS (NEP). Our results indicate that in myeloid neoplasm with erythroid predominance, patients with >20% blasts, of either NEC or ANC, share similar clinical laboratory features and survival outcomes with AML-NOS.

Proposed minimal diagnostic criteria for myelodysplastic syndromes (MDS) and potential pre-MDS conditions

Myelodysplastic syndromes (MDS) comprise a heterogeneous group of myeloid neoplasms characterized by peripheral cytopenia, dysplasia, and a variable clinical course with about 30% risk to transform to secondary acute myeloid leukemia (AML). In the past 15 years, diagnostic evaluations, prognostication, and treatment of MDS have improved substantially. However, with the discovery of molecular markers and advent of novel targeted therapies, new challenges have emerged in the complex field of MDS. For example, MDS-related molecular lesions may be detectable in healthy individuals and increase in prevalence with age. Other patients exhibit persistent cytopenia of unknown etiology without dysplasia. Although these conditions are potential pre-phases of MDS they may also transform into other bone marrow neoplasms. Recently identified molecular, cytogenetic, and flow-based parameters may add in the delineation and prognostication of these conditions. However, no generally accepted integrated classification and no related criteria are as yet available. In an attempt to address this challenge, an international consensus group discussed these issues in a working conference in July 2016. The outcomes of this conference are summarized in the present article which includes criteria and a proposal for the classification of pre-MDS conditions as well as updated minimal diagnostic criteria of MDS. Moreover, we propose diagnostic standards to delineate between ´normal´, pre-MDS, and MDS. These standards and criteria should facilitate diagnostic and prognostic evaluations in clinical studies as well as in clinical practice.

Enumerating bone marrow blasts from nonerythroid cellularity improves outcome prediction in myelodysplastic syndromes and permits a better definition of the intermediate risk category of the Revised International Prognostic Scoring System (IPSS-R)

The Revised International Prognostic Scoring System (IPSS-R) has been recognized as the score with the best outcome prediction capability in MDS, but this brought new concerns about the accurate prognostication of patients classified into the intermediate risk category. The correct enumeration of blasts is essential in prognostication of MDS. Recent data evidenced that considering blasts from nonerythroid cellularity (NECs) improves outcome prediction in the context of IPSS and WHO classification. We assessed the percentage of blasts from total nucleated cells (TNCs) and NECs in 3924 MDS patients from the GESMD, 498 of whom were MDS with erythroid predominance (MDS-E). We assessed if calculating IPSS-R by enumerating blasts from NECs improves prognostication of MDS. Twenty-four percent of patients classified into the intermediate category were reclassified into higher-risk categories and showed shorter overall survival (OS) and time to AML evolution than those who remained into the intermediate one. Likewise, a better distribution of patients was observed, since lower-risk patients showed longer survivals than previously whereas higher-risk ones maintained the outcome expected in this poor prognostic group (median OS < 20 months). Furthermore, our approach was particularly useful for detecting patients at risk of dying with AML. Regarding MDS-E, 51% patients classified into the intermediate category were reclassified into higher-risk ones and showed shorter OS and time to AML. In this subgroup of MDS, IPSS-R was capable of splitting our series in five groups with significant differences in OS only when blasts were assessed from NECs. In conclusion, our easy-applicable approach improves prognostic assessment of MDS patients.

New proposals of the WHO working group (2016) for the diagnosis of myelodysplastic syndromes (MDS): Characteristics of refined MDS types

Based on centrally diagnosed 3528 patients in the Düsseldorf registry, we validated the new proposals for the classification of the MDS by the WHO working group: 256 patients were diagnosed as MDSSLD (7,3%), 978 MDSMLD (27,7%), 227 MDS RS SLD (6,4%); 321 MDS RS MLD (9,1%), 159 MDS del(5q) (4,5%), 481 MDSEB 1 (13,6%), 620 MDSEB 2 (17,6%), and 148 MDS-U (4,2%). 352 patients (16,9% of the non blastic types) changed the category, mainly moving from RCMD to MDS RS MLD, RCUD and RCMD to MDS del(5q). Median survival times of the refined groups differed from more than 60 months in the MDSSLD (RS) groups, 37 months in the MDSMLD (RS) groups, 79 months of the MDS del(5q) group and 21 and 11 months in the MDSEB 1 and 2 groups, respectively. The difference between the groups with regard to the risk of AML evolution was also impressing. No major changes were made with regard to the MDS-U categories. In summary, the proposals of the WHO group for the classification of MDS are thoughtful, taking into account biologic parameters of the diseases, a more precise wording, to some extend pragmatic and feasible.

The uniqueness of morphological features of pure erythroid leukemia in myeloid neoplasm with erythroid predominance: A reassessment using criteria revised in the 2016 World Health Organization classification

We reviewed 97 consecutive cases of myeloid neoplasm with erythroid predominance (MN-EP) between 2000 and 2015. Following 2016 WHO classification, MN-EP patients were classified into four groups. Eight pure erythroid leukemia (PEL) (including t-MN and AML-MRC morphologically fulfilled criteria for PEL) patients had dismal outcomes (median OS: 1 month) and showed more bone marrow fibrosis, worse performance status (PS) and higher serum lactate dehydrogenase (LDH) at diagnosis than the other groups. In the univariate analysis, risks of death in MN-EP patients included the morphologic features of PEL, very poor cytogenetic risk by IPSS-R, bone marrow fibrosis, leukocytosis, anemia, hypoalbuminemia, high LDH, and poor PS. In the multivariate analysis, independent predictors of death were morphologic features of PEL (adjusted hazards ratio [HR] 3.48, 95% confidence interval [CI] 1.24–9.74, p = 0.018), very poor cytogenetic risk by IPSS-R (adjusted HR 2.73, 95% CI 1.22–6.10, p = 0.015), hypoalbuminemia (< 3.7 g/dl) (adjusted HR 2.33, 95% CI 1.10–4.91, p = 0.026) and high serum LDH (≥ 250 U/L) (adjusted HR 2.36, 95% CI 1.28–4.36, p = 0.006). Poor or unfavorable risk in different cytogenetic risk systems independently predicted death and UKMRC-R was the best model.

The effects of azacitidine on the response and prognosis of myelodysplastic syndrome and acute myeloid leukemia involving a bone marrow erythroblast frequency of >50

We reviewed the cases of 68 consecutive patients who were diagnosed with myelodysplastic syndrome (MDS, n=61) or acute erythroleukemia (AEL, n=7) according to the World Health Organization (WHO) 2008 criteria and had previously been treated with azacitidine, a hypomethylating agent. Fifteen MDS patients had bone marrow erythroblast frequencies of ≥50%, and 6 out of the 7 AEL patients were reclassified as MDS (refractory anemia with excess blasts [RAEB]-1: 1, RAEB-2: 5) according to the revised WHO 2016 criteria. There was no difference between the overall response ratio (41%), as determined by a hematological improvement in at least one of 3 lineages, of these erythroid rich patients and that of the control group, which comprised 46 MDS patients with bone marrow erythroblast frequencies of <50%. Three MDS patients that exhibited erythroid predominance achieved complete remission. The overall survival period (median: 15 months) of the erythroblast-predominant group was not inferior to that of the control group (median: 16 months). These results indicate that azacitidine is a promising treatment option for MDS/AEL irrespective of the numbers of erythroid cells in the patient's bone marrow.