Therapy-related Myeloid Malignancies Research Articles

Therapy-related myeloid malignancies in patients with multiple myeloma.

Therapy-related myeloid malignancies in patients with multiple myeloma.

Clinical Outcomes of Adults Undergoing Allogeneic Stem Cell Transplant for Secondary Acute Lymphoblastic Leukemia

Background: Secondary hematologic malignancies are increasingly recognized due to the rising number of cancer survivors. While therapy related myeloid malignancies have distinct genetic profiles and inferior allogeneic stem cell transplantation (alloHCT) outcomes, there is limited data regarding secondary acute lymphoblastic leukemia (sALL). In one report, patients with therapy related ALL had an inferior OS of 23 months after alloHCT compared to primary (pALL) where OS was not reached [Saygin et al. 2019]. In the past decade, several novel therapies have been FDA approved for adults with B-ALL allowing more patients to achieve molecular remissions prior to alloHCT, therefore, we aimed to examine the role of alloHCT for adults with sALL compared to adults with pALL in a contemporary era. Methods: We identified 247 (n= 25 sALL, n= 223 pALL) patients with ALL who underwent alloHCT at Moffitt Cancer Center from 1/2010 to 12/2022. Matching was performed with a 1:1 nearest neighbor matching on propensity score controlling for age, ALL subtype, MRD status, CR line at transplant, regimen intensity, and lines of therapy received for sALL. Three patients with sALL were excluded from matched analysis due to inability to control for selected covariates. Variable balance was assessed before and after matching. Outcomes measured included overall survival (OS), leukemia free survival (LFS), non-relapse mortality (NRM), and relapse. Survival analysis was evaluated by Kaplan-Meier estimations. Multivariate analysis was performed by Cox regression. Results: After matching, 22 patients in the pALL group and 22 patients in the sALL group were analyzed. The two groups were evenly matched for all baseline characteristics except for donor type ( Table 1 p = 0.019). The majority of patients in both groups were over the age of 40, were diagnosed with Ph(-) B-cell ALL and were transplanted in first complete remission (CR1). Cytogenetic stratification for Ph(-) patients were defined per CIBMTR criteria [Lazaryan et al. 2020]. In patients with Ph(-) sALL, cytogenetics were classified as adverse (n=4), intermediate ( n=7), favorable (n=2) and were missing in 3 patients. In the sALL group, 59% of patients had an antecedent solid tumor malignancy whereas 36% had a hematologic malignancy with one patient having two prior malignancies. Half of the sALL group (n=11) had chemotherapy exposure for primary malignancy. Median follow up time for the pALL and sALL groups was 76 and 55 months respectively. Compared to the pALL group, the sALL group did not have a significant difference in OS ( Figure 1 p = 0.3). The 2 and 5-year OS of the pALL group was 72% and 67% respectively vs. 60% and 48% in the sALL cohort (p = 0.3). The 2 and 5-year LFS of the pALL cohort was 72% and 52% respectively vs 45% and 45% of the sALL cohort (p = 0.3). Cumulative incidence of NRM (27 % vs. 18%, p=0.7) and relapse (27% vs 32% p = 1.0) were not statistically significant between sALL and pALL groups. In a multivariate analysis performed after matching, there was no associated difference in the OS (p= 0.6) between groups. Conclusion: In this study, we observed no significant difference in OS, LFS, NRM or relapse between sALL patients and pALL patients after controlling for key variables in a matched cohort analysis. Most patients included in this analysis were in complete molecular remission at time of transplant underscoring the prognostic impact of MRD. Despite 50% of the sALL cohort having exposure to prior chemotherapy, few patients had adverse cytogenetics suggesting that cytogenetic risk and MRD, and not only exposure to prior therapy are key prognostic factors for sALL patients undergoing alloHCT. Larger studies are needed to validate these findings. Despite small number of patients, we observe encouraging outcomes for this patient population with traditionally poor outcomes with conventional chemotherapy alone.

Li-Fraumeni Syndrome: The Two Faces of a Coin in Myeloid Malignancies

Background Li-Fraumeni Syndrome (LFS) is a rare, autosomal dominant genetic disorder caused by germline mutations in the TP53 tumor suppressor gene. It is characterized by a predisposition to a wide range of cancers, including hematological malignancies. Hematological malignancies account for approximately 3-4% of all LFS-related cancers of which are acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), Myelodysplastic syndromes (MDS) and lymphomas. Method and Results We retrospectively analyzed our clinical data for patients with hematological malignances from the period of Jan 2016-Jan 2022 at the national center for cancer care and research (NCCCR), the only tertiary hematology center in the country. We report on two cases with Li Fraumeni syndrome with acute leukemia and their variable spectrum of the disease manifestations and prognosis. Case 1: 16 years old male known case of rheumatic heart disease presented with double malignancy; left mandible osteosarcoma and lymphoblastic leukemia/ lymphoma concurrently in 2020. For his Leukemia he received BFM*2009 protocol and after remission he underwent surgical resection and received radiotherapy for the osteosarcoma. Patient has family history of breast cancer in his maternal aunt and his paternal great aunt. Germline Genetic testing from buccal swab revealed a pathogenic variant in TP53 gene confirming Li Fraumeni syndrome which is most likely De novo as it was not detected in both parents and his 3 siblings. In 2022 patient presented with pancytopenia and therapy related AML/MDS with complex Karyotype. He was started on salvage therapy and was planned for allogenic stem cell transplant (SCT) from his HLA matched brother, however, unfortunately, patient didn't achieve complete remission thus could not receive the SCT and he passed away one year later in 2023. Case 2: 60-year-old female known case of hypertension who was diagnosed with right breast cancer in 2011 for which she underwent surgery, chemotherapy, and radiotherapy. A year later, patient was diagnosed with left upper lobe squamous cell lung carcinoma, and underwent left upper lobectomy, chemotherapy and radiotherapy. Patient was in remission for 6 years, until 2018 when she presented with pancytopenia and therapy related AML with complex monosomic Karyotype. Due to patient's age and comorbidities, she was unfit for intensive therapy, thus she received hypomethylation agent (Azacitidine) till disease progression and was referred to genetic counseling. Patient has a family history of unknown cancer in her paternal half-sister at the age of 77 and an unknown cancer in her paternal cousin. Genetic testing reveled a mosaic pathogenic variant in TP53 gene present in 17% of the 1137 next generation sequencing reads. Shortly later, patient passed away without confirmatory fibroblast testing. Conclusion: Genetic testing indications for Li-Fraumeni syndrome present challenges as patients with full mutationin TP53 often but not always present with the full spectrum of the disease, whereas patients with mosaic profilepresent with a later onset of the disease and might not be identified early. In both scenarios, patients can be miss-identified and exposed to radiotherapy thus testing criteria warrants further evaluation. Acute Leukemia in Li-Fraumeni syndrome is associated with poor prognosis and usually presents in the context of therapy related myeloid malignancies . Identification of patients with Li-Fraumeni syndrome early on is crucial to avoid exposures to radiotherapy whenever possible thus reducing the risk of subsequent malignancies and the tragic outcomes of the disease. There are unmet clinical needs in Li-Fraumeni syndrome diagnostic and therapeutic approaches which needs further attention.

Clonal Hematopoiesis in Whole-Blood and Cell-Free DNA of Ovarian Cancer Patients Undergoing PARP-Inhibitor Treatment: An Exploratory Analysis of the ENGOT-ov48/Eudario Trial

Clonal hematopoiesis (CH), characterized by the expansion of somatically mutated hematopoietic stem cells, is an age-related phenomenon associated with the development of hematologic malignancies, increased cardiovascular risk, and other age-related proinflammatory conditions. In patients with solid tumors, cytotoxic therapies differentially select for clones with mutations in the DNA damage response (DDR) pathway, i.e. TP53 and PPM1D, leading to an elevated risk for therapy-related myeloid malignancies (t-MNs). Poly(ADP-ribose) polymerase inhibitors (PARPi) are frequently used to treat ovarian cancer with particularly high efficacy reported in tumors exhibiting homologous recombination (HR) deficiency caused by mutations in BRCA1/2 or other HR pathway genes. However, recent data indicate that PARPi treatment is also associated with an elevated risk for t-MNs. Here, we performed an in-depth analysis of CH in whole-blood (WB) and plasma of patients with relapsed high-grade ovarian cancer (HGOC) receiving platinum-based chemotherapy and PARPi treatment, elucidating the mutational landscape of CH, gene-specific dynamics, as well as the potential interference of CH with putative tumor-derived mutations in cell-free DNA (cfDNA). Serial specimen of 103 patients with relapsed, platinum-sensitive HGOC participating in the European Trial on Enhanced DNA Repair Inhibition in Ovarian Cancer (EUDARIO) study (ENGOT-ov48/NCT03783949) were analyzed using error-corrected targeted sequencing with a custom panel covering 45 myeloid and 27 HR-related genes. Study treatment consisted of six cycles of carboplatin-based chemotherapy followed by maintenance therapy with Niraparib ± the HSP90 inhibitor Ganetespib. A total of 128 somatic mutations with variant allele frequencies (VAFs) ≥ 1% were identified in 58 patients (56%) with a high fraction of DDR mutations (51 PPM1D mutations in 27 patients, 7 TP53 mutations in 7 patients). Age (median 62 years) and the number of previous therapy lines (median 1, range 1-5 lines) were significantly associated with the presence of CH. Specifically, prior exposure to PARPi treatment was strongly associated with both the presence of CH and the number of CH mutations. CH-positive patients had significantly shorter progression-free survival (median 7.9 months vs 10.6 months, p = 0.021 in log-rank test), and a trend for shorter overall survival (median 21.1 months vs 27.7 months, p = 0.16) in univariate survival analysis. With respect to adverse events, CH-positive patients more frequently had infections during study treatment (49% vs 26%, p = 0.025). All but 5 CH mutations with VAF ≥ 1% were also detectable in cfDNA with significant correlation of VAFs (R = 0.84, p < 0.0001). Mutations occurring solely in cfDNA (putatively tumor-derived) had a high fraction of TP53 and HR-related mutations, while DNMT3A and PPM1D, were rarely mutated (Figure 1). However, 23/87 (26%) of TP53 mutations and 31/98 (32%) of mutations in HR-related genes detected in cfDNA were of hematopoietic origin, underlining the importance of parallel sequencing of WB in liquid biopsies to avoid false positive results. The dynamics of CH clones under carboplatin and PARPi treatment were assessed in paired WB samples at initiation/end of treatment, which were available for 62 patients. 96 clones that initially had a VAF < 1% emerged during the treatment, including 56 PPM1D- and 10 TP53-mutated clones. Gene-wise comparison revealed a significantly higher median clonal fitness in PPM1D- and TP53-mutated clones compared to TET2- or DNMT3A-mutated clones (Figure 2). PPM1D-mutated clones exhibited lower fitness during PARPi treatment compared to carboplatin treatment (p = 0.0015 in Wilcoxon rank sum test), which was not the case for TP53-mutated clones. Finally, 8 samples with multiple mutations were subjected to single-cell genotyping on the Mission Bio Tapestri platform to investigate their clonal architecture. Preliminary data indicate clonal exclusiveness of co-occurring DDR mutations. In summary, our data reveals a high prevalence of CH in patients with relapsed HGOC and provides novel insights into the clonal architecture and dynamics of CH under carboplatin and PARPi treatment with a differential selection of DDR-driven clones. Moreover, we report a relevant interference of CH-derived mutations with tumor-derived mutations in cfDNA.

Tracking the evolution of therapy-related myeloid neoplasms using chemotherapy signatures

AbstractPatients treated with cytotoxic therapies, including autologous stem cell transplantation, are at risk for developing therapy-related myeloid neoplasms (tMN). Preleukemic clones (ie, clonal hematopoiesis [CH]) are detectable years before the development of these aggressive malignancies, although the genomic events leading to transformation and expansion are not well defined. Here, by leveraging distinctive chemotherapy-associated mutational signatures from whole-genome sequencing data and targeted sequencing of prechemotherapy samples, we reconstructed the evolutionary life-history of 39 therapy-related myeloid malignancies. A dichotomy was revealed, in which neoplasms with evidence of chemotherapy-induced mutagenesis from platinum and melphalan were hypermutated and enriched for complex structural variants (ie, chromothripsis), whereas neoplasms with nonmutagenic chemotherapy exposures were genomically similar to de novo acute myeloid leukemia. Using chemotherapy-associated mutational signatures as temporal barcodes linked to discrete clinical exposure in each patient’s life, we estimated that several complex events and genomic drivers were acquired after chemotherapy was administered. For patients with prior multiple myeloma who were treated with high-dose melphalan and autologous stem cell transplantation, we demonstrate that tMN can develop from either a reinfused CH clone that escapes melphalan exposure and is selected after reinfusion, or from TP53-mutant CH that survives direct myeloablative conditioning and acquires melphalan-induced DNA damage. Overall, we revealed a novel mode of tMN progression that is not reliant on direct mutagenesis or even exposure to chemotherapy. Conversely, for tMN that evolve under the influence of chemotherapy-induced mutagenesis, distinct chemotherapies not only select preexisting CH but also promote the acquisition of recurrent genomic drivers.

From Clonal Hematopoiesis to Therapy-Related Myeloid Neoplasms: The Silent Way of Cancer Progression.

Simple SummaryIn the last decades the improved management of cancer patients and the overall prolonged life expectancy contributed to the increased number of patients at risk of late clonal events such as therapy-related myeloid neoplasms (t-MN). The discovery of clonal hematopoiesis of indeterminate potential (CHIP) in normal individuals has shed light on the pathophysiologic mechanism behind the process of myeloid evolution, defining CHIP carriers at higher risk of progression. Moreover, different patterns of clonal evolution have been identified in case of t-MN development after anti-cancer treatment exposure. The growing body of evidence in this field allowed the creation of dedicated cancer survivorship programs and “CHIP-Clinics” in order to specifically address the issue of CHIP in patients undergoing anti-cancer treatment and develop measure of early detection possibly guiding tumor surveillance.Clonal hematopoiesis (CH) has been recognized as a predisposing factor for the development of myeloid malignancies. Its detection has been reported at different frequencies across studies, based on the type of genome scanning approach used and the population studied, but the latest insights recognize its virtual ubiquitous presence in older individuals. The discovery of CH in recent years paved the way for a shift in the paradigm of our understanding of the biology of therapy-related myeloid malignancies (t-MNs). Indeed, we moved from the concept of a treatment-induced lesion to a model where CH precedes the commencement of any cancer-related treatment in patients who subsequently develop a t-MN. Invariant patterns of genes seem to contribute to the arising of t-MN cases, with differences regarding the type of treatment received. Here, we review the principal studies concerning CH, the relationship with myeloid progression and the mechanisms of secondary t-MN development.

Hereditary cancer syndrome-associated pathogenic variants are common in patients with hematologic malignancies subsequent to primary solid cancer.

Background: As the number of long-term survivors of solid cancers keeps increasing, risk assessment of secondary hematologic malignancies is important for the prognosis of the patient. Germline genetic predisposition to secondary hematologic malignancy has been studied widely in myeloid neoplasms and rarely in lymphoid neoplasms. This study aimed to profile the mutational spectrums of patients with subsequent lymphoid tissue neoplasm to shed some light on the understudied area.Methods: In total, 39 patients who had primary solid cancer and subsequent hematologic malignancies were enrolled. We performed two next-generation sequencing (NGS) panel tests encompassing hereditary cancer predisposition genes and genes related to clonal hematopoiesis of indeterminate potential (CHIP). All statistical analyses were performed using R 3.5.1.Results: We found 8 of 39 patients with germline mutations in cancer predisposition genes; 4 of 18 patients had therapy-related myeloid neoplasms (22.2%); and 4 of 15 patients had secondary lymphoid malignancies (26.7%). Notably, of 14 patients who initially suffered from thyroid cancer, 5 patients (35.7%) had germline mutations. Malignancy of lymphoid tissue showed no association with radioactive iodine therapy but was observed to a greater extent in germline mutation-positive thyroid cancer patients regardless of their history of treatment. We observed that 24 of 39 patients (61.5%) were CHIP carriers. Patients who had secondary lymphoid malignancy were less likely to have CHIP than those who had myeloid malignancy.Conclusions: In patients with primary solid cancer who are planning to undergo cytotoxic chemotherapy, radiotherapy, or radioactive iodine therapy, an initial assessment with germline mutation testing using an expanded NGS panel, including low, moderate, and high-risk cancer-associated genes, and somatic CHIP mutation testing can screen the patients who are at risk of developing therapy-related myeloid and lymphoid malignancies. Through careful screening and monitoring throughout the treatment process, patients can benefit from the early detection of secondary malignancies and receive proper treatment.

Incidence, Risk Factors and Outcomes of Therapy-Related Myeloid Malignancies after Hematopoietic Cell Transplantation: Analysis of the Japan Society for Hematopoietic Cell Transplantation Late Complications and QOL Working Group

Background Therapy-related acute myeloid leukemia and myelodysplastic syndrome (t-AML/MDS) occur after hematopoietic cell transplantation (HCT). The incidence, risk factors and outcomes of t-AML/MDS among patients who underwent autologous or allogeneic HCT for a variety of disease have not been examined systemically. To address these questions, we conducted a retrospective cohort study using the Japanese national transplant registry database. Methods The study cohort included 43,790 patients of all ages who underwent autologous (n=24,916) or allogeneic HCT (n=18,874) for lymphoid malignancies, solid cancer and non-malignant diseases between 1977 and 2015 in Japan. Patients who had antecedent myeloid malignancies and those who had inherited disorders were excluded. Results With a median follow-up of 61 months among survivors, 354 patients developed t-AML/MDS, including 306 after autologous HCT and 48 after allogeneic HCT. The 10-year cumulative incidence of t-AML/MDS was 1.8% (95% CI, 1.6-2.0%) after autologous HCT and 0.3% (95% CI, 0.2-0.4%) after allogeneic HCT. The median patient age of t-AML/MDS diagnosis was higher in patients who had autologous HCT than those who had allogeneic HCT (59 vs 42 years, p Conclusions The incidence of t-AML/MDS was remarkably higher in patients who had autologous HCT than those who had allogeneic HCT. Risk factors and prognostic factors identified in this study would provide physicians with important information for counseling and managing patients about t-AML/MDS after HCT.

Increasing therapy-related myeloid neoplasms in multiple myeloma.

Despite the longer survival achieved in multiple myeloma (MM) patients due to new therapy strategies, a concern is emerging regarding an increased risk of secondary primary malignancies (SPMs) and how to characterize those patients at risk. We performed a retrospective study covering a 28-year follow-up period (1991-2018) in a tertiary single institution. Data of 403 MM patients were recorded and compared with the epidemiologic register of the population area covered by our centre, calculating the standardize incidence ratio (SIR) for the different types of SPMs diagnosed in the MM cohort. Fine and Gray regression models were used to identify risk factors for SPMs. Out of the 403 MM patients, 23 (5.7%) developed SPMs: 13 therapy-related myeloid (TRM) malignancies (10 of them (77%) myelodysplastic syndrome (MDS), 1 acute lymphoid leukaemia and 9 solid neoplasms. In the MM cohort, the relative risk of MDS was significantly higher than in the general population. Survival of patients with TRM malignancies was poor with a median of 4 months from the diagnosis, and most of them showed complex karyotype. Within the MM subset, multivariable analysis showed a higher risk of TRM malignancies in patients that previously received prolonged treatment with lenalidomide (>18 months). Though the improvement in MM outcome during the last decades is an unprecedented achievement, it has been accompanied by the rise in TRM malignancies with complex cytogenetic profile and poor prognosis that are in the need of an improved biologic and therapeutic approach.

Late-Onset Cytopenias and Therapy Related Myeloid Malignancies in a Cohort of Patients with Lymphoproliferative Disorders at Instituto Nacional De Cancerologia- Mexico

Background:The increasing survival rate of patients with non-Hodgkin lymphoma has allowed the diagnosis of long-term complications including therapy related myeloid malignancies (t-MDS/t-AML).Methods:To determine the frequency of late-onset cytopenias, as well as t-MDS/t-AML in patients with lymphoproliferative malignancies, a cohort followed from Jan 2011-Dec 2016 including patients with either Follicular Lymphoma (FL) or Diffuse Large B Cell Lymphoma (DLBCL) was reviewed. Inclusion criteria: patients that received full treatment at Instituto Nacional de Cancerología (INCAN), who achieved full hematologic recovery at the end of treatment, and thereafter developed any degree of cytopenia (according to the CTCAE v4.0). Exclusion criteria: Follow-up less than 6 months and previous treatment before receiving medical care at INCAN. Initially peripheral causes (vitamin deficiencies, viral infections, liver autoimmune diseases, among others) were discarded. Thereafter, bone marrow aspiration was performed for morphologic analysis (including cellularity), karyotype and FISH panel. Baseline data was compared between groups with cytopenias and without it, with X2 method. A Cox-regression model evaluated the factors involved in the development of cytopenias. Survival was estimated with Kaplan-Meier method.Results:Of 840 patients enrolled, 35 developed cytopenias (4.16%) (23-DLBCL & 12-FL). Causes of cytopenia were: medullar hypoplasia (n=4, 11.4%), transitory cytopenia (n=4, 11.4%), t-MDS (n=8, 22.8%), t-AML (n=2, 5.7%) among others. In patients with FL, only hemoglobin <12 g/dL (p=0.032) and >6 nodal areas (p=0.037) at diagnosis were statistically significant factors for the development of cytopenia; no factor was significant in patients with DLBCL. It is of interest that 80% of patients developing t-MDS also received radiotherapy. Anemia was the most frequent cytopenia in patients with DLBCL (22.8%) and pancytopenia was the most frequent in FL (54.5%). For patients with t-MDS or t-AML (table 1), there was a gender predominance in women (66.7%). Patients with complex karyotype were associated with progression to t-AML, those with t(11q23) and -7 had aggressive clinical course and shorter survival. Treatment details and outcomes are summarized in table 1.Conclusions:The incidence of t-MN is increasing as more patients survive their primary cancers. It is quite important to get further knowledge on the molecular biology of the group of therapy-related disorders not only for a better diagnostic and classification criteria, which may help in selecting individualized treatments, but also to investigate potential chemopreventive strategies. DisclosuresNo relevant conflicts of interest to declare.

Clonal haemopoiesis and therapy-related myeloid malignancies in elderly patients: a proof-of-concept, case-control study

Clonal haemopoiesis of indeterminate potential (CHIP) is an age-associated genetic event linked to increased risk of primary haematological malignancies and increased all-cause mortality, but the prevalence of CHIP in patients who develop therapy-related myeloid neoplasms is unknown. We did this study to investigate whether chemotherapy-treated patients with cancer who have CHIP are at increased risk of developing therapy-related myeloid neoplasms. We did a nested, case-control, proof-of-concept study to compare the prevalence of CHIP between patients with cancer who later developed therapy-related myeloid neoplasms (cases) and patients who did not develop these neoplasms (controls). We identified cases from our internal biorepository of 123 357 patients who consented to participate in the Total Cancer Care biobanking protocol at Moffitt Cancer Center (Tampa, FL, USA) between Jan 1, 2006, and June 1, 2016. We included all individuals who were diagnosed with a primary malignancy, were treated with chemotherapy, subsequently developed a therapy-related myeloid neoplasm, and were 70 years or older at either diagnosis. For inclusion in this study, individuals must have had a peripheral blood or mononuclear cell sample collected before the diagnosis of therapy-related myeloid neoplasm. Controls were individuals who were diagnosed with a primary malignancy at age 70 years or older and were treated with chemotherapy but did not develop therapy-related myeloid neoplasms. Controls were matched to cases in at least a 4:1 ratio on the basis of sex, primary tumour type, age at diagnosis, smoking status, chemotherapy drug class, and duration of follow-up. We used sequential targeted and whole-exome sequencing and described clonal evolution in cases for whom paired CHIP and therapy-related myeloid neoplasm samples were available. The primary endpoint of this study was the development of therapy-related myeloid neoplasm and the primary exposure was CHIP. We identified 13 cases and 56 case-matched controls. The prevalence of CHIP in all patients (23 [33%] of 69 patients) was higher than has previously been reported in elderly individuals without cancer (about 10%). Cases had a significantly higher prevalence of CHIP than did matched controls (eight [62%] of 13 cases vs 15 [27%] of 56 controls, p=0·024; odds ratio 5·75, 95% CI 1·52-25·09, p=0·013). The most commonly mutated genes in cases with CHIP were TET2 (three [38%] of eight patients) and TP53(three [38%] of eight patients), whereas controls most often had TET2 mutations (six [40%] of 15 patients). In most (four [67%] of six patients) cases for whom paired CHIP and therapy-related myeloid neoplasm samples were available, the mean allele frequency of CHIP mutations had expanded by the time of the therapy-related myeloid neoplasm diagnosis. However, a subset of paired samples (two [33%] of six patients) had CHIP mutations that decreased in allele frequency, giving way to expansion of a distinct mutant clone. Patients with cancer who have CHIP are at increased risk of developing therapy-related myeloid neoplasms. The distribution of CHIP-related gene mutations differs between individuals with therapy-related myeloid neoplasm and those without, suggesting that mutation-specific differences might exist in therapy-related myeloid neoplasm risk. Moffitt Cancer Center.

Clonal Hematopoiesis Is Associated with Therapy-Related Myeloid Malignancies in the Elderly

▪BackgroundClonal hematopoiesis of indeterminate potential (CHIP) is an age-dependent genetic event occurring in as high as 10% of individuals over age 70. Although the clinical consequence of CHIP is not well understood, it is linked to an increased risk of primary hematologic malignancies and increased all-cause mortality. A recent study reported a higher prevalence (26%) of CHIP in patients with advanced cancers (Zehir A, ASCO abstract, 2016). However, the prevalence of CHIP in patients developing therapy-related myeloid neoplasms (T-MN) is unknown. We hypothesize that chemotherapy treated cancer patients with CHIP are at higher risk for T-MN development. To address this, we conducted a nested case-control study to compare the prevalence of CHIP in cancer patients who later developed T-MN compared to those that did not. We performed sequential targeted and whole exome sequencing of T-MN cases and described clonal evolution in cases for who paired CHIP and T-MN samples were available.MethodsWe identified all patients who consented to our institutional biobanking protocol with a primary cancer preceding T-MN and an age ≥ 70 years at the time of either cancer. Chart reviews were conducted to verify that only patients who received chemotherapy and provided a blood sample before development of T-MN were included. Controls were defined as cancer patients who did not develop a subsequent malignancy and were matched to cases 4:1 on gender, primary tumor diagnosis, age, smoking status (ever/never), chemotherapy drug class, and follow-up time.DNA was isolated from peripheral blood (CHIP) or bone marrow samples (T-MN), and targeted amplicon based next-generation sequencing was performed to identify somatic mutations in genes associated with CHIP (49 genes, ThunderBolts Myeloid Panel, RainDance). Mesenchymal stem cells and CD3+ cells derived from the T-MN sample were used as independent germline controls to confirm somatic CHIP mutations. Whole exome sequencing was also performed (Agilent SureSelect XT Clinical Research Exome, Illumina NextSeq Sequencer) in paired CHIP and T-MN samples and clonal architecture was inferred using SciClone (Miller CA, PLoS Comput Biol, 2014). CHIP was defined in any sample that harbored a somatic mutation at an allele frequency of >3%.ResultsAfter screening 105,998 consented individuals from 2006 to 2016, a total of 13 patients (Figure 1a) were identified. The most common primary cancer in patients who developed T-MN was lymphoma, followed by adenocarcinoma (Table 1). The mean time to development of T-MN was 6.1 years and the mean time from the sampling date to the diagnosis of T-MN was 1.8 years. There were no statistical differences in the chemotherapy received by cases and controls (Table 1). The T-MN diagnosis was AML in 6 and MDS in 7 patients, and the majority (10/13) of patients harbored complex cytogenetics. T-MN patients had a poor overall survival (median 11 mo, Figure 1b). The prevalence of CHIP in cases and controls was higher (33%) than reported in individuals without cancer (10%), implying overlapping risk variables. Patients with T-MN had a significantly higher prevalence of CHIP prior to T-MN diagnosis when compared to matched controls (61.5% vs. 26.8%, p=0.02). The most commonly mutated gene in CHIP patients with T-MN was TP53 (36.4% vs. 5.4% in non-T-MN patients, p=0.02), while CHIP patients who did not develop T-MN more commonly harbored mutations in TET2 (35%) (Fig 1c). There was no difference in the mean allele frequencies (MAF) of CHIP mutations in cases vs. controls (9.4% vs. 14.3%, p=0.27). There was also no trend in the number or MAF of CHIP mutations observed and time to T-MN. In the majority of cases (83.3%), CHIP MAF expanded at the time of T-MN, however, a subset of paired samples (16.7%) harbored CHIP mutations that retracted giving way to expansion of a distinct mutant clone (Fig 1d).ConclusionsChip often precedes development of T-MN in chemotherapy-treated cancer patients. The distribution of CHIP-related gene mutations differs between individuals with T-MN vs. those without suggesting that there may be mutation-specific differences in T-MN risk. Further, although most CHIP mutations represented the founding leukemic mutation based on allelic frequency, some CHIP mutations retracted at the time of T-MN. These studies support the use of CHIP to inform individualized T-MN risk across cancer. [Display omitted] [Display omitted] DisclosuresKomrokji:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Speakers Bureau. Padron:Incyte: Research Funding; CTI: Research Funding; KALOBIOS: Research Funding.

Cytogenetics in Hairy Cell Leukemia at Diagnosis and Relapse: The Rate of Therapy-Related Myeloid Malignancies Is Low

Cytogenetic analysis of a large cohort of hairy cell leukemia (HCL) patients (pts) has never been reported. The influence on outcome of cytogenetic abnormalities is unknown.We retrospectively reviewed records of pts with HCL treated at Memorial Sloan Kettering Cancer Center between January 1973 and December 2013. 501 pts were identified and 331 were confirmed to have a diagnosis of HCL by histopathology or immunophenotyping. 170 patients were excluded, either because their final diagnosis was an alternate disease or there was inaccessible clinical data. Descriptive statistics were used to evaluate the cohort.260/331 (79%) were men, overall median age at diagnosis was 53 years (range 20-84 years) and median follow-up was 61 months. 241 had classical HCL and 18 had variant disease based on absent expression of CD25 by immunophenotyping or immunohistochemistry with median diagnostic WBC of 3.2x10^9/L and 8.4x10^9/L respectively. BRAF mutation testing was performed infrequently (<10% pts). In 72 pts we were unable to review immunophenotyping data to confirm disease type. 64 pts never received treatment, 156 received one line and 111 received at least 2 lines of therapy during follow up. The most common initial treatment was cladribine (n=215, 80%). Assessment of bone marrow cytogenetics was available in 105 of 331 patients (32%) at diagnosis with 92 cases of classical HCL, 8 variant HCL and 5 with unconfirmed disease type. Karyotype was normal in 95 patients (90.5%) and abnormal in 10 (9.5%). Abnormal karyotype was more common in patients with variant than classical disease, seen in 3/8 versus 7/92 respectively (p=0.007). 9/10 with abnormal karyotype had multiple clones identified including at least one cytogenetically normal metaphase. Sex chromosome loss was present in 4/10 pts (3 with loss of Y and 1 female with loss of X) while loss of genetic material from chromosome 7 was the most common autosomal abnormality (3/10 patients). The presence of an abnormal karyotype at diagnosis did not worsen survival compared to patients with a normal karyotype with an estimated 5 year OS of 100% and 97%, respectively.30/111 pts (24 classical and 6 variant HCL) who received two or more lines of therapy had cytogenetics evaluated at some point during disease relapse and 17/30 had cytogenetic abnormalities. 6 of these had cytogenetics at diagnosis and 4/6 were normal. Pts with an abnormal karyotype received more lines of therapy prior to identification of a cytogenetic abnormality than those with normal cytogenetics with a median of 3 and 1 lines respectively (p=0.008). Pts with variant HCL were more likely to have abnormal cytogenetics at relapse (6/6) than those with classical disease (11/24) (p=0.017).Cytogenetic abnormalities of all evaluable pts with relapsed HCL were reviewed. The most common abnormalities seen at relapse were monosomies or partial chromosome deletions seen in 14/17 cases. The most common abnormalities were loss of material from chromosome 7 (6/17 pts) and chromosomes 13 and 17 (4/17 pts each). Multiple abnormalities were present in 11/17 pts. No abnormality appeared to be specific for classical or variant disease. In particular loss of material from chromosome 7 was seen in both disease types. Only 2 of the 331 pts developed a therapy-related acute myeloid leukemia (t-AML) both had classical HCL. The first developed t-AML with a complex monosomal karyotype after prior treatment with cladribine, pentostatin, fludarabine and rituximab. The second had t-AML with monosomy 7 following 4 treatments with cladribine. There were no cases of myelodysplasia.In summary we identified cytogenetic abnormalities in 10% of newly diagnosed HCL pts and found that this did not adversely affect survival. Pts with variant HCL are more likely to have abnormal cytogenetics at diagnosis and at disease relapse compared to those with classical disease. Cytogenetic changes appear to be more common in those who received more lines of cytotoxic chemotherapy. Loss of material from chromosome 7 is the most common cytogenetic change seen at diagnosis and at disease progression. The rate of therapy-related myeloid malignancies is low and is not increased in HCL variant. Identification of new molecular mutations arising during disease relapse may be insightful. DisclosuresPark:Actinium Pharmaceuticals, Inc.: Research Funding; Juno Therapeutics: Consultancy.

Myelosuppression after frontline fludarabine, cyclophosphamide, and rituximab in patients with chronic lymphocytic leukemia

BACKGROUNDThe combination of fludarabine, cyclophosphamide, and rituximab (FCR) has produced improved response rates and a prolonged survival in patients with chronic lymphocytic leukemia (CLL). However, its therapeutic power is counterbalanced by significant hematologic toxicity. Persistent and new‐onset cytopenia after the completion of FCR raise concern about disease recurrence, the development of therapy‐related myeloid malignancies (TRMM), and infections.METHODSA total of 207 patients with CLL who achieved complete response, complete response with incomplete bone marrow recovery, or nodular partial remission were analyzed after frontline FCR therapy.RESULTSThree months after the completion of therapy, 35% of patients had developed grade 2 to 4 cytopenia (according to Common Terminology Criteria for Adverse Events [version 4.0]). Factors found to be associated with cytopenia at 3 months after therapy were older age, advanced Rai stage disease, and lower baseline blood counts. Moreover, patients with cytopenia were less likely to have completed 6 courses of therapy with FCR. At 6 months and 9 months after therapy, the prevalence of grade 2 to 4 cytopenia was 24% and 12%, respectively. No differences in progression‐free survival and overall survival were noted between cytopenic and noncytopenic patients or between patients with persistent and new‐onset cytopenia. The prevalence of TRMM was 2.3% and did not differ significantly between cytopenic and noncytopenic patients or between those with persistent and new‐onset disease. Late infections were more common in patients who were cytopenic at 9 months (38%) and were mostly bacterial (67%).CONCLUSIONSCytopenia after the completion of therapy is a common complication of frontline FCR that improves over time, particularly for new‐onset cases. The presence of persistent cytopenia (lasting up to 9 months after the completion of therapy) should not raise concern about CLL recurrence of the development of TRMM, but should encourage surveillance for bacterial infections for an additional 9 months. Cancer 2013;119:3805–3811. © 2013 American Cancer Society.

Acquired Therapy-Related Cytogenetic Clones in Patients Treated for Multiple Myeloma

Abstract 4059 Background:Approximately 5% of cancer patients treated with cytotoxic agents develop cytogenetic abnormalities which can progress to therapy-related myeloid malignancies over time. Acquired cytogenetic clones (ACC) have been incidentally observed in patients treated for multiple myeloma, yet their long-term clinical significance is not well defined. Patients and Methods:We performed a retrospective review of patients treated for multiple myeloma at the University of Texas MD Anderson Cancer Center over an 11-year period from 6/2001 to 6/2012. Patients with acquired cytogenetic abnormalities were identified and corresponding bone marrow biopsies at the time of detection were evaluated for the presence of therapy-related myelodysplastic syndrome (t-MDS) or acute myeloid leukemia (t-AML). Among these cases, patients with abnormal cytogenetic clones confirmed by karyotyping and/or FISH but without morphologic or clinical evidence of t-MDS/AML were classified as having silent ACC (SACC). The subsequent clinical history and bone marrow (BM) biopsies were reviewed in these patients to characterize the long-term clinical significance of SACC and the risk of developing t-MDS/AML. Results:40 patients were identified who developed abnormal cytogenetic clones while undergoing treatment for multiple myeloma. There were 29 men and 11 women with a median age of 65 years (range, 47–82) at the time of detection. The median interval from initial diagnosis of multiple myeloma to the detection of clonal abnormality was 38 months (range, 6–181). In general, patients were heavily pretreated with an average of 4.3 therapeutic regimens (range, 1–11), excluding single-agent dexamethasone, prior to the detection of clonal cytogenetic abnormalities. 37 patients (93%) had received alkylating agents while 3 patients received only bortezomib and/or lenalidomide based therapies. 31 patients (78%) had prior autologous stem cell transplantation. Abnormal cytogenetic clones identified included isolated del(20q) [n=14], complex cytogenetic abnormalities (≥3 abnormalities) [n=5], del(7q) [n=4], del(5q) [n=3], -5/del(7q) [n=2], der(1;7) [n=3], inv(3q) [n=1], der(5;15)/del(5q) [n=1], del(5q)/-7 [n=1], -7 [n=1], +8 [n=1], del(9q) [n=1], del(9p) [n=1], del (11q) [n=1], and +15 [n=1]. Bone marrow morphologic examination confirmed the presence of t-MDS in 11 (28%) patients at the time of clonal cytogenetic abnormality; 10 of these patients had aberrations of chromosome 5 or 7 and 1 had inv(3q). 29 (73%) patients met criteria for SACC, including all 14 patients with isolated del(20q). With a median follow-up of 8.7 months (range, 0–59) after the detection of SACC, only 1 of 14 patients with available follow-up BM biopsies developed t-MDS, which occurred 22 months after detection of a del(7q) SACC. Of 14 patients with SACC that had follow-up cytogenetic studies, 7 patients showed persistence of SACC, while the other 7 patients demonstrated a normal diploid karyotype. Conclusion:Among acquired cytogenetic abnormalities in patients treated for multiple myeloma, abnormalities in chromosome 5 or 7 have the highest association with the development of t-MDS/AML. However, in patients meeting the criteria for SACC, there appears to be a low-rate of progression to t-MDS/AML, especially those with isolated del(20q). Disclosures:No relevant conflicts of interest to declare.

Allogeneic hematopoietic cell transplantation outcomes for children and young adults with treatment-related myelodysplastic syndrome or acute

Objective: Therapy-related myeloid malignancies (tMDS or tAML) are well-known complications of cancer therapy for which outcomes are poor. Whether clinical characteristics can predict disease outcome in children and young adults, as they do in older adults, is not well known. Method: Twenty-five children with tMDS/tAML underwent allogeneic hematopoietic stem cell transplantation (allo-HCT) at the University of Minnesota between 1990 and 2010. Twenty-one patients received myeloablative conditioning. Graft sources included umbilical cord blood in fourteen patients [single (n=9), double (n=5)] and bone marrow in 11. Prior to transplant twenty-one patients received AML-directed chemotherapy and 19 were in complete remission at the time of allo-HCT. Twelve patients had high-risk cytogenetic abnormalities involving 11q23 (n=6), chromosome 5 (n=4) and/or chromosome 7 (n=5). Result: The 5-year OS and DFS was 23% (CI 95%: 9-41%) and 17% (CI 95%: 5-35%) respectively. Transplant related mortality (TRM) and relapse at 1-year were 39% (CI 95%: 19-59%) and 22% (CI 95%: 5-38%). We found no significant differences in survival based on remission status, pre-transplant cytogenetics or conditioning regimen. Conclusion: Outcomes of children and young adults with tMDS/tAML continue to be poor with TRM and relapse remaining the major obstacles to cure.

SIMILARITIES OF ELDERLY AND THERAPY-RELATED AML

Acute myeloid leukemia (AML) is a clonal disorder of the hematopoietic stem cell, typical of the elderly, with a median age of over 60 years at diagnosis. In AML, older age is one of the strongest independent adverse prognostic factor, associated with decreased complete response rate, worse disease-free and overall survival, with highest rates of treatment related mortality, resistant disease and relapse, compared to younger patients. Outcomes are compromised in older patients not only by increased comorbidities and susceptibility to toxicity from therapy, but it is now recognized that elderly AML has peculiar biologic characteristics with a negative impact on treatment response.In older individuals prolonged exposure to environmental carcinogens may be the basis for similarities to therapy-related myeloid malignancies (t-MN), which result from toxic effects of previous cytotoxic treatments on hematopoietic stem cells. Age is itself a risk factor for t-MN, which are more frequent in elderly patients, where also a shorter latency between treatment of primary tumor and t-MN has been reported. t-MN following chemotherapy with alkylating agents and elderly AML frequently present MDS-related cytogenetic abnormalities, including complex or monosomal karyotype, and a myelodysplastic phase preceding the diagnosis of overt leukemia. Similarly, t-MN and elderly-AML share common molecular abnormalities, such as reduced frequency of NPM1, FLT3 and CEBPA mutations and increased MDR1 expression.Given the unfavorable prognosis of elderly and t-MN and the similar clinical and molecular aspects, this is a promising field for implementation of new treatment protocols including alternative biological drugs.

A NUP98-PHF23 Transgenic Mouse Model Develops AML and T-ALL

Abstract 2467NUP98-fusions although rare, have been associated with de novo acute myeloid leukemia (AML), chronic myeloid leukemia, myelodysplastic syndrome, T-cell acute lymphoblastic leukemia (T-ALL) and therapy-related myeloid malignancies. The NUP98-PHF23 (NP23) gene fusion was cloned from an acute myeloid leukemia (AML) patient with a t(11;17)(p15;p13) chromosome translocation. The nucleoporin 98 protein (NUP98), normally a component of the nuclear pore complex, is known to be fused to at least 28 different fusion partners as a result of structural chromosomal rearrangements associated with hematological malignancies. PHF23 encodes the Plant homeodomain (PHD) finger 23 protein. PHF23 is largely uncharacterized, but the PHD finger motif has been shown to act as a reader of di- and tri-methylated histone 3 lysine 4 (H3K4me2/3) marks. This suggests that PHF23 may function in chromatin regulation and that the NP23 fusion protein may play a role in aberrant chromatin modification at domains of active gene transcription. To determine the oncogenic potential of NP23, we generated a transgenic mouse model that expressed the human fusion gene in hematopoietic tissues.We have characterized two founder lines (C10 and B10) expressing the NP23 fusion in hematopoietic tissue. Most of the offspring from the C10 line developed an AML that closely resembled the human disease, with increased blasts in the blood or bone marrow, widespread organ infiltration, and myeloid immunophenotype. Onset of disease was as early as 4.5 months, and 70 percent of the NP23 mice succumbed to leukemia by 12 months of age. Of note, an independent line (B10) developed a wider spectrum of leukemias but with similar age of onset and penetrance. The B10 mice predominantly developed T-ALL and AML, and four cases of B-ALL and one erythroleukemia, indicating that the NP23 protein was oncogenic in several different hematopoietic cell types. AMLs typically demonstrated an aberrant Mac-1+/B220dim phenotype, which has previously been recognized in leukemias caused by overexpression of the Hoxa cluster genes Hoxa5,7,9,10,11. Microarray gene expression analysis identified the Hoxa cluster genes to be markedly overexpressed, and validation by RQ-PCR demonstrated that Hoxa5, a7, a9 and a10 overexpression ranged from 10- to greater than 1000-fold increased in both the AML and T-ALL samples compared to wild type hematopoietic tissues; these Hoxa cluster genes were also overexpressed in hematopoietic tissues from clinically healthy NP23 transgenic mice. We also identified a novel transcript, Gm525 (homologue of H. sapiens C17orf67), that is markedly (100x) elevated specifically in the T-ALL samples. Most T-ALL samples have HD or PEST domain Notch1 mutations, and Notch1 mRNA levels, as well as its downstream target Hes1, are elevated in the T-ALLs compared to WT thymus. Immortal cell lines were established from two of the NP23 T-ALLs, and ChIP-seq was used to assay the genome wide pattern of H3K4me3 and H3K27me3 histone marks. Results show abundant levels of H3K4me3 at the Hoxa locus which tightly correlates to the increased Hoxa cluster gene expression seen in the cell lines. The NP23 model will be useful for identifying oncoproteins involved in leukemic transformation, particularly those oncoproteins which play a role in chromatin modification or are downstream targets of the HOXA genes. Disclosures:No relevant conflicts of interest to declare.

Patients with Therapy-Related Myeloid Disorders Share Genetic Features but Can Be Separated by Blast Counts and Cytogenetic Risk Groups Into Prognostically Relevant Subgroups,

Abstract 3583 Background:In the WHO classification of 2008, patients with therapy-related acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS) following cytotoxic therapy/radiation are combined to the category “therapy-related myeloid neoplasms”. To contribute to the discussion whether blast percentage or other subclassification are prognostically relevant in therapy-related myeloid disorders, we evaluated this combined group for clinical/genetic aspects. Study design: A total of 520 pts (242 m/278 f; median, 67.4 years; r. 18.0–91.5 yrs) with therapy-related myeloid malignancies (253 pts with ≥20% bone marrow blasts termed “t-AML”, 267 with <20% BM blasts: “t-MDS”) were investigated by cytomorphology, chromosome banding analysis, molecular genetics, and for clinical outcomes. Results: When biological characteristics of pts with ≥20% (“t-AML”) and <20% (“t-MDS”) BM blasts were compared, t-AML had higher mean WBC counts (17.7 vs 5.8×10(9)/L; p<0.001) and lower Hb (94 vs 103 g/L; p=0.003) and platelet level (81 vs 115 x10(9)/L; p=0.027) than t-MDS. Mean age was equal in t-AML/t-MDS (64.5 vs 64.6 years). Male/female ratio was lower in t-AML (0.6 vs 1.3 in t-MDS; p<0.001). Aberrant karyotypes (KTs) were more frequent in t-AML than t-MDS (175/253; 69.2% vs 147/267; 55.1%; p=0.001). NPM1 mut were similar in t-AML and t-MDS (23/197; 11.7% vs 6/54 investigated; 11.1%; p=n.s.). When only normal KTs were considered, NPM1 mut were detected in 20/65 (30.8%) t-AML (which is less than the NPM1 mut rate known in de novo NKT-AML) and were similar in NKT t-MDS (6/17; 35.3%; p=n.s.). FLT3 -ITD were less frequent in t-AML (19/210; 9.0%) compared to data on de novo AML, but more frequent than in t-MDS (2/112; 1.8%; p=0.016). Frequencies of FLT3 -ITD in normal KT were 8/66 (12.1%) in t-AML and 2/36 (5.6%) in t-MDS (p=n.s.). RUNX1 mut (t-AML: 11/81; 13.6%; t-MDS: 5/69; 7.2%), CEBPA (t-AML: 6/104; 5.8%; t-MDS: 0/10; 0.0%), FLT3- TKD (t-AML: 3/120; 2.5%; t-MDS: 0/23; 0.0%), NRAS (7/64; 10.9% vs 6/82; 7.3%), IDH (11/86; 12.8% vs 1/13; 7.7%), and MLL -PTD (7/200; 3.5% vs 5/109; 4.6%) did not differ significantly between t-AML/t-MDS. Patients with <20% BM blasts had better overall survival (OS) than pts with ≥20% BM blasts (median 43.8 vs 18.2 months; p=0.003). According to MRC cytogenetic risk groups (Grimwade et al., 2010), only 35 (6.7%) of all pts had favorable, 303 (58.3%) intermediate (t-AML: 144/253; 56.9%; t-MDS: 159/267; 59.6%), but 182 (35.0%) had adverse KTs (t-AML: 79/253; 31.2%; t-MDS: 103/267; 38.6%). In the total cohort, favorable KTs (group 1) had better OS than intermediate (group 2) and adverse (group 3) KTs (median n.r. vs 43.8 vs 16.2 months; p=0.002 comparing all 3 groups; group 1 vs 2: p=0.011; 1 vs 3: p=0.001; 2 vs 3: p=0.048). This holds true as well when t-AML pts (p=0.002 comparing different MRC groups) or t-MDS (p=0.003) were investigated separately. OS of NPM1 mut/FLT3 -ITD-neg. pts did not differ significantly from other genotypes in the total cohort (median n.r. vs 20.9 months) nor in normal KT t-AML (16.9 vs 11.0 months). In t-AML, MLL -PTD+ had worse OS than MLL -PTD-neg. pts (median 3.8 vs 16.9 months; p=0.001). In the total cohort, univariable Cox regression for OS was significant for age (p<0.001), WBC counts (p=0.016), Hb level (p=0.025), BM blasts both by a threshold of ≥20% vs <20% (p=0.003) or as continuous parameter (p=0.002), and MRC risk group (p=0.001). No significant differences were found for gender, platelets, NPM1 mut/FLT3 -ITD-negative status, or MLL -PTD+. By multivariable Cox analysis for OS age (p<0.001), WBC count (p=0.042), BM blasts by a threshold of 20% (p<0.001), and MRC risk group (p=0.002) were significant. Conclusions: In this study, patients with t-AML or t-MDS separated by a BM blast threshold of 20% showed significant differences in clinical outcomes and biological parameters. This emphasizes maintaining both subtypes within the WHO defined combined cohort of “therapy-related myeloid neoplasms”. Within both morphologically defined subentities, the karyotype is an excellent parameter for further prognostic predictions and shows similar patterns. The underrepresentation of the FLT3 -ITD and NPM1 mut in t-AML compared to de novo AML, and the similar frequency of NPM1 mut in t-AML and t-MDS suggests common molecular characteristics of both categories irrespective of blast percentages and strongly supports to combine them as therapy-related myeloid neoplasms as suggested by the WHO. Disclosures:Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Alpermann:MLL Munich Leukemia Laboratory: Employment. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

PRDM16 (1p36) translocations define a distinct entity of myeloid malignancies with poor prognosis but may also occur in lymphoid malignancies

The PRDM16 (1p36) gene is rearranged in acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) with t(1;3)(p36;q21), sharing characteristics with AML and MDS with MECOM (3q26.2) translocations. We used fluorescence in situ hybridization to study 39 haematological malignancies with translocations involving PRDM16 to assess the precise breakpoint on 1p36 and the identity of the partner locus. Reverse-transcription polymerase chain reaction (PCR) was performed in selected cases in order to confirm the partner locus. PRDM16 expression studies were performed on bone marrow samples of patients, normal controls and CD34(+) cells using TaqMan real-time quantitative PCR. PRDM16 was rearranged with the RPN1 (3q21) locus in 30 cases and with other loci in nine cases. The diagnosis was AML or MDS in most cases, except for two cases of lymphoid proliferation. We identified novel translocation partners of PRDM16, including the transcription factors ETV6 and IKZF1. Translocations involving PRDM16 lead to its overexpression irrespective of the consequence of the rearrangement (fusion gene or promoter swap). Survival data suggest that patients with AML/MDS and PRDM16 translocations have a poor prognosis despite a simple karyotype and a median age of 65 years. There seems to be an over-representation of late-onset therapy-related myeloid malignancies.