Efficacy of hypomethylating agents in therapy-related myelodysplastic syndromes

Myeloid neoplasms post cytotoxic therapy: epidemiology, pathogenesis outcomes, prognostic factors, and treatment options

Myeloid neoplasms post cytotoxic therapy (MN-pCT) are a category includes AML, MDS, and MDS/MPN arising in patients exposed to cytotoxic (DNA-damaging) therapy for an unrelated condition in 2022 version World Health Organization (WHO) classification. With improved survival of patients with tumors, the incidence of MN-pCT after chemotherapy and/or radiation therapy among patients with tumors has gradually risen. However, the outcome of MN-pCT is poorer than that of primary myeloid neoplasms. This review summarizes the current understanding based on existing research, as a foundation for further research on MN-pCT.

Cancer epigenetics: from laboratory studies and clinical trials to precision medicine

Epigenetic dysregulation is a common feature of a myriad of human diseases, particularly cancer. Defining the epigenetic defects associated with malignant tumors has become a focus of cancer research resulting in the gradual elucidation of cancer cell epigenetic regulation. In fact, most stages of tumor progression, including tumorigenesis, promotion, progression, and recurrence are accompanied by epigenetic alterations, some of which can be reversed by epigenetic drugs. The main objective of epigenetic therapy in the era of personalized precision medicine is to detect cancer biomarkers to improve risk assessment, diagnosis, and targeted treatment interventions. Rapid technological advancements streamlining the characterization of molecular epigenetic changes associated with cancers have propelled epigenetic drug research and development. This review summarizes the main mechanisms of epigenetic dysregulation and discusses past and present examples of epigenetic inhibitors in cancer diagnosis and treatment, with an emphasis on the development of epigenetic enzyme inhibitors or drugs. In the final part, the prospect of precise diagnosis and treatment is considered based on a better understanding of epigenetic abnormalities in cancer.

Prolonged haematologic toxicity in CAR-T-cell therapy: A review

Chimeric antigen receptor-T-cell (CAR-T-cell) therapy is a novel immunotherapy with encouraging results for treatment of relapsed/refractory haematologic malignancies. With increasing use, our understanding of immune-mediated side effects such as cytokine release syndrome and neurotoxicity has improved; nevertheless, prolonged haematologic toxicity (PHT), with a high incidence rate, remains underrecognized. Owing to heterogeneity in populations, the CAR-T cells used and diseases treated as well as differences in the definition of PHT, its rate, risk factors and management vary across studies. In this review, we provide a narrative of PHT occurring in patients following CAR-T-cell therapy; evidence of PHT treatment strategies is also presented, with the aim of contributing to systematic understanding of PHT.

Secondary myeloid neoplasms after CD19 CAR T therapy in patients with refractory/relapsed B-cell lymphoma: Case series and review of literature

Background

Several chimeric antigen receptor T cells (CAR T) targeting CD19 have induced profound and prolonged remission for refractory/relapsed (R/R) B-cell lymphoma. The risk of secondary malignancies, especially myeloid neoplasms, is of particular concern in the CAR T community, which still remains unclear.

Methods

Four patients with R/R B-cell lymphoma after CD19 CAR T therapy diagnosed with secondary myeloid neoplasms (SMN) from 2 hospitals in eastern China were presented, including 3 with myelodysplastic syndrome (MDS) and 1 with acute myeloid leukemia (AML). Using single-cell RNA sequencing (scRNA-seq), we compared the cellular components of bone marrow (BM) samples obtained from one of these MDS patients and a health donor. We also provided a review of recently published literature concerning SMN risk of CAR T therapy.

Results

Relevant demographic, clinical, laboratory, therapeutic and outcome data were collected and presented by chart review. In our case series, the male-female ratio was 3.0 and the median age at MDS onset was 61.25 years old (range, 50-78). Median number of previous systemic therapies was 4.5 (range, 4-5), including autologous hematopoietic stem cell transplantation (auto-HSCT) in one patient. BM assessments prior to CAR T therapy confirmed normal hematopoiesis without myeloid neoplasms. Moreover, for 3 patients with SMN in our series, cytogenetic analysis predicted a relatively adverse outcome. In our experience and in the literature, treatment choices for the patients with SMN included allogeneic hematopoietic stem cell transplantation (allo-HSCT), hypomethylating agent (HMA), period filgrastim, transfusions and other supportive care. Finally, treatment responses of lymphoma, together with SMN, directly correlated with the overall survival of this community. Of note, it appeared that pathogenesis of MDS wasn't associated with the CAR T toxicities, since all 4 patients experienced a pretty mild CRS of grade 1-2. Additionally, scRNA-seq analysis described the transcriptional alteration of CD34+ cells, identified 13 T/NK clusters, and also indicated increased cytotoxic T cells in MDS BM.

Conclusion

Our study illustrated the onset and progression of SMN after CD19 CAR T therapy in patients with R/R B-cell lymphoma, which provides useful information of this uncommon later event.

Clinicopathologic and Molecular Analysis of Normal Karyotype Therapy-Related and De Novo Acute Myeloid Leukemia: A Multi-Institutional Study by the Bone Marrow Pathology Group

PURPOSE

Therapy-related acute myeloid leukemias (t-AML) are a heterogenous group of aggressive neoplasms that arise following exposure to cytotoxic chemotherapy and/or ionizing radiation. Many therapy-related myeloid neoplasms (t-MN) are associated with distinct chromosomal aberrations and/or TP53 alterations, but little is known about the clinicopathologic and molecular features of normal karyotype t-AML (NK-t-AML) and whether this t-MN subtype is distinctly different from NK de novo AML (NK-dn-AML).

METHODS

This multi-institutional study by the Bone Marrow Pathology Group retrospectively evaluated clinicopathologic and molecular characteristics of 335 patients with NK-AML, comprising 105 t-AML and 230 dn-AML cases.

RESULTS

Patients with t-AML compared with dn-AML exhibit significantly shorter overall survival (OS; median months: 17.6 v 44.2; P < .0001) and relapse-free survival (RFS; median months: 9.1 v 19.2; P = .0018). Frequency of NPM1, FLT3, KRAS, and GATA2 mutations were significantly different in NK-t-AML compared with NK-dn-AML (NPM1 35% v 49%; P = .0493; FLT3 23% v 36%; P = 0494; KRAS 12% v 5%; P = .0465; GATA2 9% v 2% P = .0105), while TP53 mutations were rare. Patients with t-AML more often stratified into intermediate or adverse 2017 ELN genetic risk groups. Favorable ELN risk predicted favorable OS (hazard ratio [HR], 0.4056; 95% CI, 0 to 0.866; P = .020) and RFS (HR, 0.355; 95% CI, 0 to 0.746; P = .006). Among all patients with NK-AML, stem-cell transplant and favorable ELN risk both significantly affected RFS, while therapy-relatedness and age had a borderline significant impact on OS (HR, 1.355; 95% CI, 0.975 to 1.882; P = .070).

CONCLUSION

To our knowledge, this is the largest study to date to comprehensively evaluate NK-t-AML and provides a framework that may inform our understanding of NK-t-AML disease biology and could potentially help guide therapeutic management and improved disease classification in t-MNs that lack cytogenetic aberrations.

Role Of TP53 mutations in predicting the clinical efficacy of hypomethylating therapy in patients with myelodysplastic syndrome and related neoplasms: a systematic review and meta-analysis

Hypomethylating agents (HMAs) are now a major treatment option for myelodysplastic syndrome (MDS) and related neoplasms, but 50% of patients still do not respond and realize poor outcomes. Mutational predictors of treatment efficacy attract continuous attention. Whether TP53 mutations can be used as predictors of HMA effectiveness has caused heated debate. Therefore, we performed a meta-analysis to investigate the predictive value of TP53 mutations to outcomes of HMA therapy in patients with MDS and related neoplasms. We systematically searched PubMed, Embase, the Cochrane Library, and the WanFang databases (published deadline: September 12, 2019). The primary endpoints were overall response rate (ORR) and overall survival (OS). Odds ratio (OR), hazard ratio (HR), and 95% confidence intervals (CI) were pooled to estimate the association between TP53 mutations and the clinical efficacy of HMAs. Four hundred fifteen papers were found, and 22 papers were included in this meta-analysis (N = 2020 participants). The results showed that the presence of TP53 mutation predicted an increased overall response rate with HMA treatment in the subsets that restricted patients in de novo disease, MDS by WHO (World Health Organization) criteria, or NGS (next-generation sequence) group (P = 0.005, P = 0.003, P = 0.0005, respectively). However, TP53 mutations remained poor factors for OS (P < 0.00001). Collectively, in HMA therapy, TP53 mutations can predict better ORR when setting more refined subgroups, but TP53 mutations still strongly correlated with poor survival in hypomethylating therapy.

Clonal selection in therapy-related myelodysplastic syndromes and acute myeloid leukemia under azacitidine treatment

INTRODUCTION

Therapy-related myelodysplastic syndrome and acute myeloid leukemia (t-MDS/AML) are defined as complications of previous cytotoxic therapy. Azacitidine (AZA), a hypomethylating agent, has showed activity in t-MDS/AML.

OBJECTIVES

We evaluated the clonal dynamics of AZA-treated t-MDS/AML.

METHODS

We collected bone marrow samples, at diagnosis and during treatment, from AZA-treated t-MDS/AML patients. NGS on 19 myeloid genes was performed, and candidate mutations with a variant allele frequency >5% were selected.

RESULTS

Seven t-AML and 12 t-MDS were included with median age of 71 (56-82) years old, median number of AZA cycles of 6 (1-15), and median overall survival (OS) of 14 (3-29) months. We observed correlation between AZA response and clonal selection. Decrease of TP53-mutated clone was correlated with response to AZA, confirming AZA efficacy in this subgroup. In some patients, emergence of mutations was correlated with progression or relapse without impact on OS. Clones with mutations in genes for DNA methylation regulation frequently occurred with other mutations and remained stable during AZA treatment, independent of AZA response.

CONCLUSION

We confirmed that the molecular complexity of t-MNs and that the follow-up of clonal selection during AZA treatment could be useful to define treatment combination.

Therapy-related myeloid neoplasms: clinical perspectives

Therapy-related myeloid neoplasms (t-MNs) are a complication of cytotoxic treatment for primary tumors and autoimmune diseases. t-MNs result from a complex interaction between individual predisposition and exposition to toxic agents. Some different biological and clinical characteristics can be recognized according to the type of anticancer drug. Compared to de novo myeloid neoplasms, prognosis of t-MN is dismal. Age and karyotype are the most important prognostic factors for t-MN, which should be treated with frontline chemotherapy treatments that are appropriate for patients with myelodysplastic syndrome (MDS) and de novo acute myeloid leukemia (AML) with similar disease characteristics. Allogeneic stem cell transplantation should be considered particularly for unfavorable karyotypes and younger patients with aggressive disease.

Allogeneic Hematopoietic Stem Cell Transplantation In Therapy-Related Myeloid Neoplasms (t-MN) of the Adult: Monocentric Observational Study and Review of the Literature

Background

Therapy related myeloid neoplasms (t-MN) occur due to direct mutational events of chemotherapeutic agents and radiotherapy. Disease latency, mutational events and prognosis vary with drugs categories.

Methods

We describe a cohort of 30 patients, 18 females and 12 males, with median age of 52.5 years (range, 20 to 64), submitted to allogeneic stem cell transplantation (HSCT) in our department between September 1999 and March 2017. Patients had a history of solid tumour in 14 cases, haematological disease in 15 cases and both of them in one case. After a median of 36.5 months (range, 4 to 190) from first neoplasm, patients developed t-AML in 19 cases and t-MDS in 11 cases. Molecular abnormalities were detected in 5 patients, while karyotype aberrations were found in 17 patients. Patients received conventional chemotherapy in 14 cases, azacitidine in 10 cases and both of them in one case. Five patients were submitted to HSCT without previous treatment except for supportive therapy.

Results

Seventeen patients obtained sustained CR after SCT, while 8 patients showed resistant or relapsed disease. The remaining five patients died early after SCT. At follow up time (May 2017) 13 patients were alive with a median OS of 48 months (range 3–195), while 17 patients died after a median of 4 months (range 1–27) by relapse mortality in 6 cases and non-relapse mortality in the other 11 patients.

Conclusions

Global OS was 43%. After SCT, 72.2% of patients with t-MN maintained a sustained CR.

Efficacy of single-agent decitabine in relapsed and refractory acute myeloid leukemia

Improving therapy for relapsed/refractory AML remains a challenge. We performed a retrospective analysis of outcomes following decitabine treatment in 34 patients with relapsed/refractory AML (median age, 62; median Charlson comorbidity score, 6). Decitabine, 20 mg/m² daily, was given in 5- (25%) or 10-day (75%) cycles. Overall response rate (OR) was 30% with 21% complete remission and 9% partial remission rate. Patients with therapy-related myeloid neoplasm (t-MN) and secondary AML had a significantly higher OR compared to those with de novo AML (70 vs. 30%; p = .02). Median overall survival of all patients was 8.5 months. Median survival in patients with t-MN or secondary AML was 12.4 months compared to 8 months in those with de novo AML (p = .20). Fifteen (44%) patients proceeded to hematopoietic stem cell transplant. These data support using 10-day treatment cycles of decitabine in patients with relapsed/refractory AML, particularly for those with secondary or therapy-related AML.

Comparison of clinical outcomes and prognostic utility of risk stratification tools in patients with therapy-related vs de novo myelodysplastic syndromes: a report on behalf of the MDS Clinical Research Consortium

While therapy-related (t)-myelodysplastic syndromes (MDS) have worse outcomes than de novo MDS (d-MDS), some t-MDS patients have an indolent course. Most MDS prognostic models excluded t-MDS patients during development. The performances of the International Prognostic Scoring System (IPSS), revised IPSS (IPSS-R), MD Anderson Global Prognostic System (MPSS), WHO Prognostic Scoring System (WPSS) and t-MDS Prognostic System (TPSS) were compared among patients with t-MDS. Akaike information criteria (AIC) assessed the relative goodness of fit of the models. We identified 370 t-MDS patients (19%) among 1950 MDS patients. Prior therapy included chemotherapy alone (48%), chemoradiation (31%), and radiation alone in 21%. Median survival for t-MDS patients was significantly shorter than for d-MDS (19 vs 46 months, P<0.005). All models discriminated survival in t-MDS (P<0.005 for each model). Patients with t-MDS had a significantly higher hazard of death relative to d-MDS in every risk model, and had inferior survival compared to patients with d-MDS within all risk group categories. AIC Scores (lower is better) were 2316 (MPSS), 2343 (TPSS), 2343 (IPSS-R), 2361 (WPSS) and 2364 (IPSS). In conclusion, subsets of t-MDS patients with varying clinical outcomes can be identified using conventional risk stratification models. The MPSS, TPSS and IPSS-R provide the best predictive power.

Use of 5-azacitidine for therapy-related myeloid neoplasms in patients with concomitant active neoplastic disease

BACKGROUND

Patients diagnosed with therapy-related myeloid neoplasms (TRMN) with concomitant active neoplastic disorder (CAND) are usually proposed for best supportive care (BSC). We evaluated the feasibility of using 5-azacytidine (AZA) in this setting.

METHODS

All patients referred to Gustave Roussy between 2010 and 2015 for TRMN diagnosis (less than 30% blast) and eligible for AZA treatment were included. Patients with CAND proposed for BSC were also described. Patient's outcomes were analyzed based on the presence or not of a CAND.

RESULTS

Fifty-two patients with TRMN were analyzed, including 19 patients with CAND (14 eligible for AZA) and 33 without CAND eligible for AZA. The 5 patients with CAND ineligible for AZA had a worst performance status (p=0.016) at diagnosis and a shorter overall survival (OS) (0.62 months). Baseline characteristics of patients eligible for AZA were similar in the 2 groups except a trend for best performance status in patients with CAND (p=0.06). Overall response rate (71.4% vs 60.3%), transfusion independence (50.0% vs 45.5%) and OS (12.7 months vs 10.8 months) were similar between patients with and without CAND respectively (p=ns).

CONCLUSION

Here we report the feasibility and efficacy of AZA for selected patients with TRMN and a CAND.

Therapy-related myeloid neoplasms: does knowing the origin help to guide treatment?

Therapy-related myeloid neoplasms (t-MN) combine t-MDS and therapy related acute myeloid leukemia (t-AML) patients in one entity because of their similar pathogenesis, rapid progression from t-MDS to t-AML, and their equally poor prognosis. Treatment with epipodophyllotoxins like etoposide has been associated with a short interval between treatment and development of t-AML, with fusion oncogenes like KMT2A/MLL-MLLT3 and a better prognosis. In contrast, treatment with alkylating agents has been associated with a longer latency, an initial MDS phase, adverse cytogenetics, and a poor prognosis. The pathogenesis of t-MN can be explained by direct induction of an oncogene through chromosomal translocations, induction of genetic instability, or selection of a preexisting treatment-resistant hematopoietic stem cell clone. Recent evidence has highlighted the importance of the last mechanism and explains the high frequency of TP53 mutations in patients with t-MN. After previous cytotoxic therapy, patients present with specific vulnerabilities, especially evident from the high nonrelapse mortality in patients with t-MN after allogeneic hematopoietic cell transplantation. Here, the prognostic impact of currently known risk factors and the therapeutic options in different patient subgroups will be discussed.

Therapy-related myeloid neoplasms: does knowing the origin help to guide treatment?

Therapy-related myeloid neoplasms (t-MN) combine t-MDS and therapy related acute myeloid leukemia (t-AML) patients in one entity because of their similar pathogenesis, rapid progression from t-MDS to t-AML, and their equally poor prognosis. Treatment with epipodophyllotoxins like etoposide has been associated with a short interval between treatment and development of t-AML, with fusion oncogenes like KMT2A/MLL-MLLT3 and a better prognosis. In contrast, treatment with alkylating agents has been associated with a longer latency, an initial MDS phase, adverse cytogenetics, and a poor prognosis. The pathogenesis of t-MN can be explained by direct induction of an oncogene through chromosomal translocations, induction of genetic instability, or selection of a preexisting treatment-resistant hematopoietic stem cell clone. Recent evidence has highlighted the importance of the last mechanism and explains the high frequency of TP53 mutations in patients with t-MN. After previous cytotoxic therapy, patients present with specific vulnerabilities, especially evident from the high nonrelapse mortality in patients with t-MN after allogeneic hematopoietic cell transplantation. Here, the prognostic impact of currently known risk factors and the therapeutic options in different patient subgroups will be discussed.

Therapy-related myelodysplastic syndromes, or are they?

The incidence of therapy-related myelodysplastic syndromes (t-MDS) is increasing as the number of cancer survivors is increasing. While t-MDS is currently defined descriptively by prior receipt of chemotherapy and/or radiotherapy, some forms of MDS that occur post localized radiation monotherapy, biologically and clinically resemble de novo (d)-MDS more than t-MDS, and therefore may not be truly therapy-related. Although patients with t-MDS, as a group, fare worse than patients with d-MDS, a variation in individual outcomes of patients with t-MDS has increasingly been appreciated. As such, accurate risk stratification is important for counseling of patients and for clinical decision making. Most of the current clinical tools used for prognostication in t-MDS were developed for d-MDS and were not specifically validated in patients with t-MDS. The management of patients with t-MDS remains challenging, highlighting the importance of developing effective prevention strategies as well as newer, targeted, and rationally-designed therapeutic interventions.

Therapy-related myeloid neoplasms: what's in a name?

PURPOSE OF REVIEW

Therapy-related myeloid neoplasms (tMN) are increasingly recognized and studied diseases which have traditionally been defined clinically. With advances in methods used to study the genetics of aging and myeloid disease biology, novel insights are emerging which are expected to improve our understanding of the genetics and pathogenesis of tMN.

RECENT FINDINGS

Clinical outcomes in tMN and de novo MDS/AML appear to be largely determined by genetics, and data are emerging to show how DNA mutations may enhance tMN risk stratification. The discovery of skewed hematopoieses and mutations in healthy older adults suggests an alternate predisposition mechanism for the genesis of tMN. Patients with tMN do respond to standard therapy and can benefit from allogeneic transplant in a manner similar to their genetically matched de novo counterpart.

SUMMARY

De novo MDS/AML and tMN have shared genetic features, and tMN clinical outcomes may depend more on the genetics at presentation than the clinical history of an antecedent malignancy. Acquired somatic mutations in genes such as TP53 and myeloid skewing with associated mutations in cancer-free older adults may predispose such individuals to tMN under the influence of myelosuppressive therapy, and this may be a route to the development of a subset of tMN.

Therapy-related myeloid neoplasms - what have we learned so far?

Therapy-related myeloid neoplasms are neoplastic processes arising as a result of chemotherapy, radiation therapy, or a combination of these modalities given for a primary condition. The disease biology varies based on the etiology and treatment modalities patients receive for their primary condition. Topoisomerase II inhibitor therapy results in balanced translocations. Alkylating agents, characteristically, give rise to more complex karyotypes and mutations in p53. Other etiologies include radiation therapy, high-dose chemotherapy with autologous stem cell transplantation and telomere dysfunction. Poor-risk cytogenetic abnormalities are more prevalent than they are in de novo leukemias and the prognosis of these patients is uniformly dismal. Outcome varies according to cytogenetic risk group. Treatment recommendations should be based on performance status and karyotype. An in-depth understanding of risk factors that lead to the development of therapy-related myeloid neoplasms would help developing risk-adapted treatment protocols and monitoring patients after treatment for the primary condition, translating into reduced incidence, early detection and timely treatment.

The clinical importance of moderate/severe bone marrow fibrosis in patients with therapy-related myelodysplastic syndromes

The presence of moderate to severe bone marrow (BM) fibrosis has been shown to be an adverse feature in patients with primary myelodysplastic syndromes (MDS). However, the clinical importance of BM fibrosis is not clear in therapy-related MDS. We retrieved all therapy-related MDS (t-MDS) cases (n = 266) diagnosed at our hospital over a 10-year period (2003-2012). Reticulin and trichrome stains were performed in cases in which BM fibrosis was suspected on initial evaluation of hematoxylin and eosin-stained slide. BM fibrosis was graded according to European consensus guidelines, and a score of MF2/MF3 was defined as moderate/severe fibrosis. Moderate/severe BM fibrosis was found in 47 (17%) patients. Compared to 219 patients with no/mild BM fibrosis, the patients with moderate/severe fibrosis presented with severer thrombocytopenia (p = 0.039) and higher numbers of circulating blasts (p = 0.051) but with similar degrees of anemia and neutropenia, transfusion requirements, and similar incidences of hepatosplenomegaly and constitutional symptoms. Histological examination revealed a comparable BM cellularity and BM blast percentage, but markedly increased megakaryocytes (p < 0.001) in the fibrotic group. Although the risk distribution of cytogenetic data was similar according to the New Comprehensive Cytogenetic Scoring criteria, -5 and -17 were more frequently observed in t-MDS with moderate/severe BM fibrosis (p = 0.031 and p = 0.043, respectively). With a median follow-up of 11.5 months, patients with moderate/severe BM fibrosis showed a similar risk of acute myeloid leukemia transformation and a comparable overall survival in univariate and multivariate analyses. Moderate/severe BM fibrosis in patients with t-MDS is associated with certain clinicopathological and genetic features. However, unlike the situation in patients with primary MDS, moderate/severe BM fibrosis does not add additional risk to patients with therapy-related MDS.

Recent advances in the management of therapy-related myelodysplastic syndromes and acute myeloid leukemia

PURPOSE OF REVIEW

Therapy-related myelodysplastic syndromes and acute myelogenous leukemia (t-MDS/AML) comprise an increasingly common, poor-risk disease cohort without standard treatment options. This review describes available treatments and recent advances that may influence the clinical management of t-MDS/AML.

RECENT FINDINGS

Multiple retrospective studies have identified poor-risk cytogenetics, chemotherapy resistance, comorbidities from prior cancer and therapy, and persistence of the primary malignancy as factors that contribute to poor clinical outcomes of t-MDS/AML. Recent analyses show that t-MDS/AML can respond to standard therapy, but responses are less durable. In most cases, cure is made more likely with allogeneic stem cell transplantation. These findings suggest that improved survival may result from earlier, low-intensity nontransplant therapy, and aggressive pursuit of reduced-intensity transplant approaches in eligible individuals coupled with posttransplant relapse prevention strategies. Molecular characterization of t-MDS/AML may aid future clinical management decisions and identify targets for therapy.

SUMMARY

Data emerging from recent t-MDS/AML studies are shedding light on factors that contribute to disease biology and poor clinical outcomes. These findings can be used to develop strategies to improve the treatment and survival of patients with t-MDS/AML.

5-Aza-2'-deoxycytidine causes replication lesions that require Fanconi anemia-dependent homologous recombination for repair

5-Aza-2′-deoxycytidine (5-azadC) is a DNA methyltransferase (DNMT) inhibitor increasingly used in treatments of hematological diseases and works by being incorporated into DNA and trapping DNMT. It is unclear what DNA lesions are caused by 5-azadC and if such are substrates for DNA repair. Here, we identify that 5-azadC induces DNA damage as measured by γ-H2AX and 53BP1 foci. Furthermore, 5-azadC induces radial chromosomes and chromatid breaks that depend on active replication, which altogether suggest that trapped DNMT collapses oncoming replication forks into double-strand breaks. We demonstrate that RAD51-mediated homologous recombination (HR) is activated to repair 5-azadC collapsed replication forks. Fanconi anemia (FA) is a rare autosomal recessive disorder, and deaths are often associated with leukemia. Here, we show that FANCG-deficient cells fail to trigger HR-mediated repair of 5-azadC-induced lesions, leading to accumulation of chromatid breaks and inter-chromosomal radial fusions as well as hypersensitivity to the cytotoxic effects of 5-azadC. These data demonstrate that the FA pathway is important to protect from 5-azadC-induced toxicity. Altogether, our data demonstrate that cytotoxicity of the epigenetic drug 5-azadC can, at least in part, be explained by collapsed replication forks requiring FA-mediated HR for repair.

Azacitidine in the treatment of therapy related myelodysplastic syndrome and acute myeloid leukemia (tMDS/AML): a report on 54 patients by the Groupe Francophone Des Myelodysplasies (GFM)

The effect of azacitidine (AZA) in therapy related MDS and AML (t-MDS/AML) is not well established. 54 patients (42 t-MDS and 12 t-AML), 71% of whom had complex karyotype, received AZA for at least one cycle (median 4 cycles). The overall response rate (ORR) was 39% in the whole cohort and 62% in patients who received ≥4 cycles. One, 2 and 3 year OS was 36%, 14% and 8% respectively. Female gender (p=0.01) and ECOG 0-1 (p=0.04) were associated with significantly better OS, while karyotype and marrow blast percentage had no significant impact. By comparison with de novo MDS/AML treated in the same program, t-MDS/AML had a similar response rate (38% vs 45% in de novo MDS/AML, p=0.53), but significantly shorter OS (2 year OS of 14% vs 33.9%, p=0.0005). However, in a multivariate analysis performed in all patients (de novo and therapy related cases), only complex karyotype and high IPSS, and not etiology (i.e. de novo versus therapy related), had a significant impact on OS. Nine (15%) patients received allogeneic stem cell transplantation, 4 of whom were still alive.

Mutational analysis of therapy-related myelodysplastic syndromes and acute myelogenous leukemia

Therapy-related myelodysplastic syndromes and acute myelogenous leukemia comprise a poor-risk subset of myelodysplastic syndromes and acute myelogenous leukemia. Large-scale mutation profiling efforts in de novo myelodysplastic syndromes have identified mutations that correlate with clinical features, but such mutations have not been investigated in therapy-related myelodysplastic syndromes and acute myelogenous leukemia. Genomic DNA from 38 patient samples were subjected to high throughput polymerase chain reaction and sequenced for TP53, TET2, DNMT3A, ASXL1, IDH1, IDH2, EZH2, EED, SUZ12, RBBP4, SRSF2, U2AF35, and SF3B1. We identified somatic mutations in 16 of 38 (42%) patients. TP53 mutations were the most common lesion, detected in 8 of 38 (21%) patients, followed by TET2 in 4 of 38 (10.5%). Cases with a TP53 mutation or loss of the TP53 locus had a worse overall survival compared to those with wild-type TP53 (8.8 vs. 37.4 months; P=0.0035).

Outcome of azacitidine treatment in patients with therapy-related myeloid neoplasms with assessment of prognostic risk stratification models

Azacitidine's efficacy in therapy-related myeloid neoplasms (t-MN) has not been well-studied. In our retrospective review of 84 t-MN patients treated with azacitidine, median overall survival (OS) was 14.5 months and overall response rate was 43%, including 11% complete remission, 4% marrow complete remission, and 11% partial remission. In patients who underwent allogeneic transplant (25%), median OS was 19.2 versus 12.8 months (P=0.023) for those who did not. Response rates were comparable to those reported for de novo myelodysplastic syndrome. When we analyzed outcomes according to five scoring systems, only the Global MD Anderson Risk Model predicted survival with statistical significance.