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Background: Lenalidomide maintenance therapy post-autologous stem cell transplantation (ASCT) is associated with improved progression-free survival (PFS) and possibly overall survival in multiple myeloma (MM). However, almost all patients do relapse as a result of residual multiple myeloma cells that remain after the high-dose chemotherapy. In the myeloma setting it has been found that the hedgehog (Hh) pathway is essential for maintaining a subset of tumor causing stem cells. LDE 225 (Sonidegib) is a potent selective oral bioavailable antagonist of Smoothened (SMO), a component of the Hh signaling pathway. In in vitro experiments, LDE225 treatment of myeloma cell lines resulted in a modest inhibition of cell proliferation at increasing doses. When LDE225 was combined with lenalidomide, a more than additive effect was observed in terms of cell proliferation, an effect that was more pronounced in the context of myeloma cell lines growing in co-culture with marrow derived stromal cells. These findings form the basis of evaluation of LDE 225 as a strategy to enhance the activity of lenalidomide in the post-transplant maintenance setting. The minimal residual state post SCT provides the most optimal situation for evaluation of a drug that is likely to work by inhibiting the tumor cells that escaped high dose therapy. Methods: Multiple myeloma patients without evidence of progression, who were 60 - 120 days after a single autologous stem cell transplant (SCT), performed within 1 year of diagnosis were eligible for the study. Maintenance therapy was started approximately 3 months after SCT. Treatment consisted of lenalidomide 10 mg days 1-21 and LDE225 400 mg days 1-28 in 28-day cycles for a total of 18 cycles. The goal of the study was to assess toxicity of this combination, complete response rate (CR) progression free survival (PFS) at 1 and 2 year and overall survival (OS). CR and PFS were estimated using an exact binomial distribution and Kaplan Meier curves respectively. Results: A total of 28 patients were accrued from Jan 2014 to Aug 2016, 1 patient canceled prior to treatment and 1 patient was deemed ineligible resulting in 26 evaluable pts for CR and PFS. The median age of all pts (n=26) was 60 years (range 43-69) and 50% were males. Seventy-three percent of patients reported one treatment regimen prior to SCT, while 27% reported 2 or more prior regimens. The other characteristics of the patient are summarized in Table 1. Twenty seven pts received at least one cycle of treatment and are evaluable for toxicities (AE). Patients were treated for a median of 12.5 (range 1-18) cycles. While 10 pts (38.5%) completed protocol treatment (18 cycles), the remaining 16 pts went off treatment due to AEs (6, 23%), disease progression (3, 11.5%), refusal of further treatment (3, 11.5%) and other reasons (4, 15.4%). A grade 3 or higher AE at least possibly attributed to either drug was seen in 63%. Grade 3+ hematologic toxicities were noted in 30%, with 7% neutropenia and 4% thrombocytopenia. Notable grade 2+ non-hematologic toxicities with more than 5% incidence were dysgeusia 22%, alopecia 11%, and anorexia 7%. Grade 3+ non-hematologic toxicities were fatigue, myalgia and arthralgia each at 7%. The CR rate in evaluable patients was 46% (5 CRs and 7 sCRs) with a 95% CI of 27% - 66%. CR rate improved from 31% to 46%. VGPR or better improved from 42% to 85%. The 24-month PFS (time from SCT to progression or death due to any cause) was 73% (95% CI: 57.9 - 92.3%) with a median time to censoring of 38 months. Conclusion: Lenalidomide in combination with LDE225 as posttransplant maintenance therapy was associated with some toxicity but manageable. The combination improved the depth of response after autologous stem cell transplant. Long-term follow-up is needed to determine overall survival. Disclosures Lacy: Celgene: Research Funding. Dispenzieri:Celgene: Research Funding; Takeda: Research Funding; Pfizer: Research Funding; Janssen: Consultancy; Intellia: Consultancy; Akcea: Consultancy; Alnylam: Research Funding. Gertz:Ionis: Honoraria; Alnylam: Honoraria; Prothena: Honoraria; Celgene: Honoraria; Spectrum: Honoraria, Research Funding; Janssen: Honoraria. Kapoor:Glaxo Smith Kline: Research Funding; Amgen: Research Funding; Janssen: Research Funding; Cellectar: Consultancy; Takeda: Honoraria, Research Funding; Celgene: Honoraria; Sanofi: Consultancy, Research Funding. Dingli:alexion: Consultancy; Janssen: Consultancy; Millenium: Consultancy; Rigel: Consultancy; Karyopharm: Research Funding. Russell:Imanis: Equity Ownership. Kumar:Janssen: Consultancy, Research Funding; Takeda: Research Funding; Celgene: Consultancy, Research Funding. OffLabel Disclosure: Sonidegib (LDE 225) is a selective oral bioavailable antagonist of Smoothened (SMO), a component of the hedgehog signaling pathway.

Abstract Pathogenic sequence variants (PSV) in BRCA1 or BRCA2 (BRCA1/2) are associated with increased risk and severity of prostate cancer. We evaluated whether PSVs in BRCA1/2 were associated with risk of overall prostate cancer or high grade (Gleason 8+) prostate cancer using an international sample of 65 BRCA1 and 171 BRCA2 male PSV carriers with prostate cancer, and 3,388 BRCA1 and 2,880 BRCA2 male PSV carriers without prostate cancer. PSVs in the 3′ region of BRCA2 (c.7914+) were significantly associated with elevated risk of prostate cancer compared with reference bin c.1001-c.7913 [HR = 1.78; 95% confidence interval (CI), 1.25–2.52; P = 0.001], as well as elevated risk of Gleason 8+ prostate cancer (HR = 3.11; 95% CI, 1.63–5.95; P = 0.001). c.756-c.1000 was also associated with elevated prostate cancer risk (HR = 2.83; 95% CI, 1.71–4.68; P = 0.00004) and elevated risk of Gleason 8+ prostate cancer (HR = 4.95; 95% CI, 2.12–11.54; P = 0.0002). No genotype–phenotype associations were detected for PSVs in BRCA1. These results demonstrate that specific BRCA2 PSVs may be associated with elevated risk of developing aggressive prostate cancer. Significance: Aggressive prostate cancer risk in BRCA2 mutation carriers may vary according to the specific BRCA2 mutation inherited by the at-risk individual.

PURPOSE Recent trials have shown potential benefit of extended adjuvant endocrine therapy and relatively high risk of recurrence (RoR) after 5 years in hormone receptor-positive (HR+) human epidermal growth factor receptor 2–negative (HER2−) breast cancer. Although risk of late relapse in HR+ HER2− breast cancer is fairly well defined, the risk in HER2-positive (HER2+) breast cancer treated with adjuvant trastuzumab-based chemotherapy remains largely unknown. METHODS We included 3,177 patients with HER2+ breast cancer treated with adjuvant chemotherapy alone or with trastuzumab from the North Central Cancer Treatment Group N9831 (ClinicalTrials.gov identifier: NCT00005970 ) and National Surgical Adjuvant Breast and Bowel Project B-31 (ClinicalTrials.gov identifier: NCT00004067 ) trials. RESULTS Overall, HR+ breast cancer was significantly associated with improved recurrence-free survival (RFS) during the first 5 years (hazard ratio, 0.65; 95% CI, 0.56 to 0.77; P < .001). Among patients treated with trastuzumab, cumulative hazard for RFS was lower in patients with HR+ HER2+ breast cancer during the first 5 years (10.96% v 17.48%; hazard ratio, 0.60; 95% CI, 0.45 to 0.79; P < .001). However, there was no significant difference in RFS based on HR status during years 5 to 10 (hazard ratio, 1.32; 95% CI, 0.93 to 1.88; P = .12). A comparable degree of trastuzumab benefit was observed in HR+ and HR− breast cancers ( P for interaction = .87). Furthermore, we observed low RoR in years 5 to 10 among patients with HR+ HER2+ breast cancer: 3.23% in patients without lymph node involvement (N0) and 6.39% in patients with involvement of one to three lymph nodes (N1). CONCLUSION The benefit of adjuvant trastuzumab persists for a long time. A distinct pattern of recurrence was observed between HR+ and HR− HER2+ disease but with similar degree of benefit from adjuvant trastuzumab. RoR in years 5 to 10 in HR+ HER2+ breast cancer is low, particularly in patients with N0 or N1 disease.

Abstract Background: Currently, low molecular weight heparin is the guideline endorsed treatment of patients with cancer associated venous thromboembolism (VTE). While apixaban is approved for the treatment of acute VTE, there are limited data supporting its use in cancer patients. Methods: Patients with cancer associated acute VTE were randomly assigned to receive either apixaban 10 mg twice daily for 7 days followed by 5 mg twice daily or subcutaneous dalteparin (200 IU/kg for 1 month followed by 150 IU/kg once daily) for 6 months. The primary outcome was major bleeding. Secondary outcomes included VTE recurrence and a composite of major plus clinically relevant non-major bleeding. Results: Of the 300 patients who underwent randomization, 287 were included in the primary analysis. Of these, metastatic disease was present in 65.5% of subjects and 74% were receiving concurrent systemic cancer therapy. Colorectal, lung, pancreas, and breast cancers were the four most prevalent cancer types. Major bleeding occurred in 0 of the 142 patients (0%) in the apixaban group as compared with 3 of the 145 patients (2.1%) in the dalteparin group (p=0.9956). Recurrent VTE occurred in 5 patients (3.4%) in the apixaban group and 20 patients (14.1%) in the dalteparin group (difference in risk -10.7 percentage points) with a Hazard Ratio (HR) 0.26, (95% CI, 0.09 - 0.80, p = 0.0182). Major plus clinically relevant non-major bleeding were similar at 9% for both groups. There were no mortality differences comparing apixaban (15.9%) and dalteparin (10.6%) groups at 6 months (HR 1.36, 95% CI 0.79 - 2.35). Monthly quality of life surveys favored apixaban therapy for many measures including: concern for excess bruising, stress, irritation, burden of delivery, and overall satisfaction with anticoagulant therapy (p<0.05). Monthly bruising questionnaire favored apixaban at each interval (p<0.002). Conclusions: Oral apixaban therapy was associated with very low rates of bleeding and significantly lower VTE recurrence with superior quality of life outcome measures compared to parenteral dalteparin in the treatment of cancer associated VTE. These data support the clinical utility of apixaban for the acute treatment of VTE in this patient population. Table. Table. Disclosures No relevant conflicts of interest to declare.

Abstract Background: New targeted therapies continue to show improved efficacy in various stages of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), sparing patients from chemoimmunotherapy. However, cure remains elusive. Here, we present a front-line alternative based on a combination of high-dose methylprednisolone (HDMP) and ofatumumab, followed by consolidative therapy with lenalidomide plus ofatumumab. Methods: This is a phase II, single-center study in patients with treatment-naive (TN) CLL/SLL. During the first treatment phase (cycles 1-3) patients received HDMP 1000 mg/m2 IV and ofatumumab 2000 mg (300 mg given week 1 then 2000 mg for a total of 12 doses) IV infusions weekly x 4 doses in cycle 1 of a 28 day cycle, then every 2 weeks for cycles 2 and 3. During the second treatment phase (cycles 4-12), patients received renally adjusted lenalidomide 5-10 mg daily and ofatumumab 2000mg IV once every 8 weeks. Growth factor support was permitted at the discretion of treating physician. Prophylactic medications included allopurinol for tumor lysis syndrome (TLS) 3 days before C1D1 through C1; and trimethoprim/sulfamethoxazole and fluconazole through cycle 4, and acyclovir through C12. Patients received aspirin 81 mg/day as thrombosis prophylaxis while on lenalidomide. Patients were assessed for response by iwCLL 2008 criteria (including imaging assessment) after completion of cycles 3 and 12. The study allowed continuation of lenalidomide if patients achieved complete (CR), partial (PR) response or stable disease (SD). Primary endpoints were efficacy, adverse events (AEs) profile, and time-to-treatment failure (TTF). Results: Between January 2012 and September 2015, the study enrolled a total of 45 patients. Median follow-up was 50.4 (5.6-72.8) months. The median age was 62.6 (48.2-86.1) years. Chromosomal analysis by FISH demonstrated Del17p in 8 (17.8%), Del11q (+/- others, except Del17p) in 10 (22.2%), Trisomy 12 (+/- others, except Del17p and Del11q) in 8 (17.8%), Del13q in 10 (22.2%), no mutations in 9 (20%) patients. The IGHV status was unmutated in 34 (75.6%) cases. Indications to start treatment were: symptomatic lymphadenopathy, symptomatic splenomegaly, anemia, and thrombocytopenia in 5 (11.1%), 10 (22.2%), 12 (26.7%), and 18 (40%), respectively. The median duration of treatment was 35.6 (2.7-66.9) months. Reasons for treatment discontinuation were: progressive disease (PD) in 9 (20%), AEs in 15 (33.3%), transplantation in 3 (6.7%), consent withdrawal in 1 (2.2%), and secondary malignancies in 2 (4.4%) cases. The overall response rates (PR+CR) at 3, 12, 24, 36, and 48 months were 75.6%, 77.8%, 66.7%, 44.4%, and 37.8%, respectively. The CR rates at 3, 12, 24, 36, and 48 months were 2.2%, 11.1%, 20%, 17.8%, and 13.3% respectively. Fifteen patients remain in PR/CR and on treatment at the time of this analysis. The intention-to-treat median TTF was 45.2 (2.9-69.7) months, and was not different among high risk groups such as Del17p, Del11q and/or unmutated IgHV. In patients who discontinued for reasons other than PD the median duration of response without treatment was 30.7 (9.8-69.7) months. Three (6.7%) patients underwent allogeneic hematopoietic cell transplantation after a median of 3 (3 - 4) treatment cycles. Treatment was well tolerated with grade 3/4 infusion reaction in 1 (2.2%) patient. Grade 3/4 treatment-related hematological AEs were neutropenia, thrombocytopenia, and anemia in 33 (73.3%), 5 (11.1%), and 1 (2.2%), respectively. Grade 3/4 infections occurred in 6 (13.3%) patients. No grade 3/4 tumor flares were observed, and there were no cases of TLS or thrombosis. Conclusion: The combination of ofatumumab, HDMP and lenalidomide is effective and well tolerated in treatment-naive CLL/SLL, even when poor prognostic features are present. Disclosures Komrokji: Novartis: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Celgene: Honoraria, Research Funding; Novartis: Honoraria, Speakers Bureau; Celgene: Honoraria, Research Funding; Novartis: Honoraria, Speakers Bureau. Locke:Novartis Pharmaceuticals: Other: Scientific Advisor; Cellular BioMedicine Group Inc.: Consultancy; Kite Pharma: Other: Scientific Advisor. Kharfan-Dabaja:Seattle Genetics: Speakers Bureau; Incyte Corp: Speakers Bureau; Alexion Pharmaceuticals: Speakers Bureau. Sokol:Spectrum Pharmaceuticals: Consultancy; Seattle Genetics: Consultancy; Mallinckrodt Pharmaceuticals: Consultancy.

Abstract Background: Obesity is increasing in prevalence worldwide and has potential implications on chemotherapy dosing and selection of patients for therapy. Auto HCT improves outcomes for patients with MM, but optimal chemotherapy dosing for obese patients is poorly defined. Methods: We identified 1087 patients reported to the CIBMTR between 1995 and 2003 who underwent auto HCT for MM as part of initial therapy, defined as within 18 months of diagnosis, and received high-dose melphalan conditioning, with or without total body irradiation (TBI). We categorized patients by body mass index (BMI) as normal (18.5– 24.9), overweight (25–29.9), obese (30–34.9), or severely obese (≥35). Underweight patients (BMI <18.5, N=9) were excluded from analysis. We analyzed overall survival (OS) and progression-free survival (PFS) from date of transplant, using Kaplan-Meier curves and the log-rank test for univariate analyses and using Cox proportional hazards models for multivariate analyses. Results: Cases were reported from 114 centers in 10 countries. There were 292 patients of normal weight (27%); 472 were overweight (43%), 198 were obese (18%), and 125 severely obese (11%). Median follow-up of survivors was 63, 61, 60 and 59 months, respectively. Significant baseline differences among BMI groups indicate that obese patients selected for transplant were younger (median age 58, 58, 56, and 55 years, respectively, p=0.005) and had less severe disease at diagnosis, with lower bone marrow plasmacytosis and less frequent renal failure, hypercalcemia, and severe anemia. Obese patients received higher total melphalan doses but lower doses per square meter of body surface area (calculated based on actual body weight). Univariate analyses show no significant effect of BMI category on either OS or PFS. However, among patients who received TBI as part of conditioning, multivariable analyses show a significant effect of BMI on PFS (p-value for interaction 0.006). In this subgroup, a higher BMI was associated with longer PFS (p=0.006, Figure 1). Among patients who received melphalan alone, no effect of BMI was apparent (Figure 2). The difference in PFS for patients receiving melphalan/TBI was due to a decreased risk of relapse among obese patients. Pairwise comparisons of conditioning regimen (TBI vs. no TBI) within BMI categories showed significant reduction in risk of treatment failure for obese (HR=0.54, p=0.04) and severely obese (HR=0.32, p=0.001) patients who received TBI. No differences in OS were apparent in multivariate analyses. Relative risks (RR) for PFS from a multivariable model adjusting for possible confounders are shown below: TBI No TBI n RR (95% CI) P n RR (95% CI) P Normal 44 1.00 Poverall=0.006 248 1.00 Poverall=0.18 Overweight 62 0.92 (0.60–1.40) 0.69 405 0.90 (0.75–1.08) 0.24 Obese 21 0.49 (0.27–0.90) 0.021 177 0.85 (0.68–1.07) 0.16 Severely obese 22 0.39 (0.20–0.76) 0.005 100 1.12 (0.86–1.45) 0.42 Conclusion: Obesity, when measured by BMI, has no statistically significant effect on OS among patients with myeloma receiving high-dose melphalan. Among patients receiving melphalan with TBI, a higher BMI is associated with improved PFS. The reason for the restriction of this effect to TBI-containing conditioning regimens requires further investigation. The current common strategy of reducing melphalan doses (i.e. calculating based on ideal or adjusted body weight) does not appear to impair outcomes for obese patients. Obesity should not exclude patients from consideration of autologous transplantation. Figure Figure

Abstract Multiple Myeloma (MM) is the most common indication for autologous hematopoietic stem cell transplantation (auto HCT). However, little information is available regarding the outcome of patients (pts) with the rarer immunoglobulin subtypes IgD and IgM, which represent 2% and 0.5%, respectively, of all MM cases. In addition, IgD MM has been reported previously to have a poorer prognosis, at least after conventional therapy. The CIBMTR conducted a retrospective analysis of MM pts transplanted between 1995–2005 to describe the characteristics and results of auto HCT in IgD (n=36) and IgM (n=11) among 3578 MM patients with auto HCT during this period. Median follow-up of survivors was 41 (range 2–130) months for pts with IgD and 58 (range 5–101) months for those with IgM MM. Among pts with IgD subtype, median age was 52 years (yrs), 67% were male, 36% had a creatinine >2 mg/L, 61% had Durie-Salmon stage III disease at diagnosis and 33% had Kappa Serum Light chain; the corresponding values for IgM pts were 58 yrs, 36%, 73% and 55% respectively. Prior to auto HCT, 75% of IgD pts were chemosensitive and 25% had received >2 lines of chemotherapy, while all IgM pts were chemosensitive and none had received more than 2 lines of prior therapy. Median time from diagnosis to auto HCT was 9 months in both subtypes. The most common conditioning regimen was singleagent melphalan, and all but 1 pt with IgD disease were grafted with blood stem cells. The small sample size precluded multivariate analysis for potential prognostic factors for outcome. Below table summarizes the post-auto HCT results in these pts contrasted with a reference pool of IgG and IgA MM receiving auto HCT in the same time period. Outcomes, probability (95% CI) IgD IgM IgG/IgA (n=36) (n=11) (n=1475) 100-day mortality, % 0 9 ( 0 – 32) 7 (5 – 8) Non MM deaths, % @ 1 yr 0 9 (0 – 32) 5 (4 – 7) @ 3 yrs 3 (0 – 13) 21 (2 – 51) 16 (14 – 18) Relapse/ Progression, % @ 1 yr 21 (9 – 37) 20 (2 – 49) 18 (16 – 20) @ 3 yrs 59 (41 – 76) 32 (8 – 64) 36 (34 – 39) Progression-free survival, % @ 1 yr 79 (63 – 91) 71 (41 – 93) 77 (74 – 79) @ 3 yrs 38 (21 – 56) 47 (17 – 78) 47 (44 – 50) Overall survival, % @ 1 yr 87 (74 – 97) 91 (68 – 100) 79 (77 – 85) @ 3 yrs 69 (51 – 84) 68 (36 – 93) 53 (50 – 57) No striking differences are apparent in the post auto HCT outcomes of patients with IgD and IgM MM. These results are also consistent with published outcomes of pts with IgD/ IgM MM (Wechaleker et al Ann Hematol. 2005 Feb; 84(2):115–7; Maisner et al Bone Marrow Transplant. 2008 Jan; 41(1):51–4).

Abstract Background Hip and knee arthroplasty (THA and TKA), in general, pose a high risk for venous thromboembolism (VTE), and pharmacologic VTE prophylaxis is often strongly recommended. In patients (pt) with hemophilia undergoing THA/TKA, given the underlying bleeding diathesis, the routine use of pharmacologic VTE prophylaxis is controversial. In this study, we report THA/TKA outcomes in pt with hemophilia in our institution. Methods Retrospective chart review of Mayo Comprehensive hemophilia center pt undergoing THA and TKA. Medical records were reviewed for objectively documented VTE for up to 3 months after surgery. Results 42 consecutive pt with hemophilia A (n=38) or B (n=4) underwent 71 operations: THA (n=32) and TKA (n=39) over a period of 39 years. All pt received compression stockings up to 6 weeks after surgery; 6/71 (8.4%) received sequential intermittent compression and 2/71 (2.8%) received postoperative low molecular weight heparin (LMWH). Symptomatic femoral vein DVT occurred in 1/42 pt (2%); (1/71, 1.4% of operations (1.4%)), 10 days after THA for traumatic hip fracture and after the LMWH was discontinued. The patient was subsequently found to be heterozygous for the factor V Leiden gene mutation. For up to 3 months after surgery, there were no additional cases of symptomatic DVT. There was no unexpected bleeding in the 2 patients receiving LMWH. Conclusion In this this study, routine use of compression stockings without the use of pharmacologic prophylaxis resulted in a low rate of symptomatic VTE in patients with hemophilia. This may be similar to the incidence in the general population receiving LMWH (Heit, JA et al Annals of Internal Medicine 2000) A limited sample size precludes definitive recommendations for practice. For appropriate high risk patients, limited use of pharmacologic prophylaxis may still be important. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 680 Cytogenetics play an essential role in determining the prognosis of patients with AML. However, there is still no validated cytogenetics grouping scheme that specifically applies to patients undergoing allogeneic stem cell transplantation, which hampers accurate prognostication and risk stratification. We studied 821 adult patients (median age 41, range 18–74) who underwent SCT between 1999 and 2004 for AML (excluding APL) in CR1 or CR2 and who were reported to the CIBMTR from centers with >20 patients meeting study criteria. 75% of patients received a myeloablative conditioning. 496 patients had a normal karyotype. The primary cytogenetics reports were manually reviewed for 92% of the patients with an abnormal karyotype. We compared the ability of the 6 existing grouping schemes (MRC, CALGB, EORTC/GIMEMA, SWOG/ECOG, DFCI, and Monosomal Karyotype (MK) classifications) to stratify patients, using both the Akaike Information Criterion in multivariable models and the C-statistic. Among all existing schemes, the DFCI system provided a marginally superior stratification for overall and leukemia-free survival. We also built a new classification using individual cytogenetic abnormalities in a Cox model that included other significant covariates (performance status, therapy-related disease, conditioning intensity, graft source, donor match, duration of CR1, and gender match). This CIBMTR scheme (see Table), which is similar to the DFCI scheme except for the inclusion of patients with t(8;21) in the intermediate group, could stratify patients into 3 groups with similar treatment-related mortality but significantly different overall survival, leukemia-free survival, and incidence of relapse. This scheme appeared to apply to both patients in CR1 and in CR2 (see FiguresF2). This transplant-specific scheme could be adopted for prognostication purposes and to stratify patients with karyotypic abnormalities entering transplantation clinical trials. Future studies may clarify the relative outcome of patients with t(8;21) and refine this scheme with the inclusion of molecular abnormalities. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: The 2016 revision to the World Health Organization (WHO) classification of myeloid neoplasms has specifically categorized germline mutations that are associated with myeloid clonal evolution (Arber et al. Blood 2016). This group consists of myeloid neoplasms with an isolated germline predisposition (CEBPA, DDX41), myeloid neoplasms associated with congenital thrombocytopenia (ETV6, RUNX1, ANKRD26) and germline myeloid neoplasms with multi-organ dysfunction (GATA2, chromosomal breakage disorders, telomere biology disorders etc). We carried out this study to describe the clinical spectrum of germline disorders with predisposition to myeloid neoplasms as categorized by the 2016 WHO classification revision. Methods: After Institutional Review Board (IRB) approval, the adult and pediatric bone marrow failure syndrome database (1990-2016) and the electronic medical record were queried for germline disorders involving GATA2, CEBPA, DDX41, ETV6, RUNX1, ANKRD26, Down syndrome and Noonan syndrome. Chromosomal breakage assays (Diepoxybutane/Mitomycin-C), flow-fluorescent in-situ hybridization (FISH) for telomere length assessment, Fanconi anemia complementation assays and Sanger/Next Generation sequencing (NGS) for the aforementioned germline disorders with myeloid predisposition were carried out in Clinical Laboratory Improvement Amendments (CLIA)-certified laboratories. These disorders were then classified based on the 2016 WHO classification revision. Results : 54 individuals (37 families) were included in the study. Eleven (20%) patients belonging to 5 families were identified as having germline mutations with a preexisting platelet disorder: ETV6 (n=1), ANKRD26 (n=5), RUNX1 (n=5). Forty-three (79%) patients (32 families) had inherited syndromes with multi-organ dysfunction: GATA2 (n=11, 26%), bone marrow failure syndromes (n=14, 33%) and telomere biology disorder (n=14, 33%). There was one patient with neurofibromatosis with a germline PTPN11 mutation who developed juvenile myelomonocytic leukemia, while there were three patients with Down syndrome; 2 with transient abnormal myelopoiesis and one who developed acute megakaryocytic leukemia. The clinical phenotype, prevalence and characteristics of myeloid clonal evolution and outcomes are presented in Table 1. No patients with germline CEBPA or DDX41 mutations were identified. Patients with germline platelet disorders did not have any prominent non-hematological manifestations. Erythrocytosis (20%) with long-standing thrombocytopenia (100%) was a unique feature associated with ANKRD26 mutations. Non-hematologic clues such as human papillomavirus (HPV)-driven warts, primary lymphedema (Emberger syndrome) and frequent atypical infections with monocytopenia were seen in patients with germline GATA2 mutations, and preceded myeloid clonal evolution (morphologic, cytogenetic and molecular). Notably, the age at presentation and penetrance of myeloid transformation was variable, with individuals from the same family developing symptoms during the first decade of life and others remaining asymptomatic to date (fifth decade). Somatic ASXL1 mutations were detected in all 3 (100%) patients with GATA2 mutations and in one patient with ANKRD26 mutation that developed myeloid clonal evolution. In our study myeloid clonal evolution was seen in 40% with RUNX1 mutations, 27% with GATA2 mutations, and 20% with ANKRD26 mutations. We could not calculate the same for bone marrow failure syndromes as the total number of cases seen are still being assessed. Outcomes with allogeneic stem cell transplantation were favorable in appropriately selected patients (Table 1). Conclusion : The 2016 WHO revision to the classification of myeloid neoplasms highlights the importance of recognition and molecular characterization of germline mutations (syndromic and non-syndromic) with risk for myeloid clonal evolution. While some of these disorders (GATA2, Fanconi anemia, telomere biology disorders) may have important non-hematological clues, many present with isolated thrombocytopenia (RUNX1, ETV6). The age and frequency of myeloid evolution is highly variable. Acquisition of somatic ASXL1 mutations at the time of clonal myeloid transformation highlights the role of epigenetic dysregulation in disease evolution. Disclosures Kenderian: Novartis: Patents & Royalties, Research Funding.