Abstract: To investigate the efficacy and toxicities of CPX-351 outside a clinical trial, we analyzed 188 patients (median age 65 years, range 26–80) treated for therapy-related acute myeloid leukemia (t-AML, 29%) or AML with myelodysplasia-related changes (AML-MRC, 70%). Eighty-six percent received one, 14% two induction cycles, and 10% received consolidation (representing 22% of patients with CR/CRi) with CPX-351. Following induction, CR/CRi rate was 47% including 64% of patients with available information achieving measurable residual disease (MRD) negativity ( 〈 10 −3 ) as measured by flow cytometry. After a median follow-up of 9.3 months, median overall survival (OS) was 21 months and 1-year OS rate 64%. In multivariate analysis, complex karyotype predicted lower response ( p  = 0.0001), while pretreatment with hypomethylating agents ( p  = 0.02) and adverse European LeukemiaNet 2017 genetic risk ( p   〈  0.0001) were associated with lower OS. Allogeneic hematopoietic cell transplantation (allo-HCT) was performed in 116 patients (62%) resulting in promising outcome (median survival not reached, 1-year OS 73%), especially in MRD-negative patients ( p  = 0.048). With 69% of patients developing grade III/IV non-hematologic toxicity following induction and a day 30-mortality of 8% the safety profile was consistent with previous findings. These real-world data confirm CPX-351 as efficient treatment for these high-risk AML patients facilitating allo-HCT in many patients with promising outcome after transplantation.

Abstract: Abstract 3281 Poster Board III-1 Introduction: In the two consecutive German CML studies III and IIIA (recruitment periods from 1995 to 2001 and 1997 to 2004), eligible patients were assigned to early HSCT by genetic randomization according to availability of a matched related donor. After randomization, 113 patients of study III (84% of 135) and 144 of study IIIA (87% of 166) were eventually transplanted in first chronic phase (CP) using a related donor. Despite comparable transplantation protocols and most centers participating in both studies, survival probabilities in study IIIA were significantly better, even when adjusted for the established EBMT risk score (Gratwohl et al., Lancet 1998 [1]), p + 0.0097. For further explanation, the German Registry for Stem Cell Transplantation (DRST) and the Swiss Transplant Working Group for Blood and Marrow Transplantation (STABMT) were asked for data support. Patients and Methods: The main sample characteristics of the 257 transplanted CML study patients were also applied to the registry patients: diagnosis of CML between 1994 and 2004, first HSCT with a related donor performed in first CP between 1995 and 2004 at an age between 12 and 65 years, and blood or bone marrow as stem cell sources. Thus, additional data of 582 HSCT patients were retrieved from the two registries. Age, recipient sex, donor sex, time between diagnosis and HSCT, calendar year of HSCT, stem cell source, and HLA matching were investigated as potential predictive factors for survival. Then, a sample of patients with the same risk distribution as the 113 patients of study III was randomly drawn from the registry patients. By application of repeated resampling to this new patient group, bootstrap confidence intervals for survival probabilities at various times after HSCT were extractable. This provided the basis to judge whether the survival in study III could be seen as a typical random representation of a sample with an equivalent risk structure or not. The same method was applied to the 144 patients of study IIIA. Results: The 5-year survival probability of all 839 patients resulted in 73% (229 died). Median follow-up time of living patients was 6.7 years. Due to the characteristic plateau of post-transplant survival probabilities, the predictive influence was judged by the Kaplan-Meier method and the log rank statistic. Also consideration of age and time between diagnosis and HSCT as continuous variables seemed less appropriate than working with categorizations. Furthermore, the previously published cut-points “1 year” for time from diagnosis to HSCT ([1] ) and “44 years” for age at HSCT (Maywald et al., Leukemia 2006) were independently confirmed to be the best. Cox model and logistic regression with survival status after 3 years both indicated that age at HSCT, HLA matching, time between diagnosis and HSCT, and calendar year of HSCT had independent statistically significant predictive influence on survival (p 〈 0.05). The first two factors had the strongest effects. Calendar year was only influential when distinction was made between HSCT until and after 1999. All possible combinations of the 4 factors could be summarized in 4 risk groups with significantly different survival probabilities (at 5 years: 87%, 76%, 63%, and 24%). Matched for the risk group distribution of study III [study IIIA], a maximum of 290 [428] registry patients could be drawn. For the 290 [428] patients, 5-year survival was 69% [77%] with a 95% bootstrap confidence interval from 63% to 74% [72% to 81%]. Thus, as for all yearly intervals within the first 5 years, the 5-year survival probabilities of studies III: 65% and IIIA: 79% lied within the corresponding confidence intervals. Conclusions: Along with the registry patients, the study data enabled the identification of age at HSCT, HLA matching, time between diagnosis and HSCT, and calendar year of HSCT as factors with independent predictive impact on survival which led to 4 risk groups with statistically significantly different survival probabilities. More favorable-risk patients in study IIIA stood for a better transplantation strategy. In consideration of these different risks, the survival probabilities in both studies did not significantly vary from those of registry samples with matched risk structures. Accordingly, an improved transplantation strategy along with random variation could be considered as an explanation of the significantly different survival probabilities between the two studies. Disclosures: Haferlach: MLL Munich Leukemia Laboratory: Equity Ownership. Hochhaus:Novartis, Bristol-Myers Squibb: Research Funding. Hasford:Novartis: Research Funding. Gratwohl:AMGEN, Roche, Bristol-Myers Squibb, Novartis, Pfizer: Research Funding; Novartis: Consultancy. German CML Study Group:Kompetenznetz Leukämie, European Leukemia Net, Roche, Essex, AMGEN: Research Funding.

Abstract: Background In a recent phase-III trial CPX-351 (Jazz Pharmaceuticals, Palo Alto, CA), a liposomal encapsulation of cytarabine and daunorubicin, has shown higher remission rates and longer overall survival (OS) in patients aged 60 to 75 years with AML with myelodysplasia-related changes (AML-MRC) or therapy-related AML (t-AML) in comparison to conventional 7+3 regimen. Based on this CPX-351 has been approved in the USA 2017 and in Europe 2018 for adult patients with newly-diagnosed AML-MRC or t-AML. Still, several issues such as age ( & lt;60 years), measurable residual disease (MRD), molecular subgroups and outcome after allo-HCT were not addressed in the phase-III trial. Aiming to investigate these open aspects and to provide more clinical experience with CPX-351, we performed a real-world analysis of patients with AML treated with CPX-351 as first-line therapy. Design/Methods: For this retrospective analysis, we collected data on baseline characteristics, treatment details including allo-HCT and outcome from patients with newly-diagnosed AML-MRC or t-AML, who were treated with CPX-351 according to the EMA label between 2018 and 2020 in 25 German centers participating in the Study Alliance Leukemia (SAL), German Cooperative Transplant Study Group and the AML Study Group (AMLSG). Results: A total of 188 patients (median age 65 years, range 26 to 80) with t-AML (29%) or AML-MRC (70%) including 46 patients (24%) & lt;60 years could be analyzed. Eigthy-six percent received one, 14% two induction cycles and 10% received consolidation with CPX-351. Following induction, CR/CRi rate was 47% including 64% of patients with available information achieving measurable residual disease (MRD) negativity ( & lt;10-3) as measured by flow cytometry at local laboratories. Additionally, 35 patients were categorized as MLFS at first remission control, which achieved CRi (n=16) or CR (n=10) in the further course without additional therapy. After median follow-up of 9.3 months, median overall survival (OS) was 21 months and 1-year OS rate was 64%. In multivariate analysis, complex karyotype predicted lower response (p=.0001), and pretreatment with hypomethylating agents (p=.02) and adverse European LeukemiaNet 2017 genetic risk (p & lt;.0001) were associated with lower OS. Allo-HCT was performed in 116 patients (62%) including 101 of these patients with CR prior transplant and resulted in 1-year OS of 73% (median survival not reached), especially in MRD negative patients (p=.048). With 69% of patients developing grade III/IV non-hematologic toxicity following induction and a day 30-mortality of 8% the safety profile was consistent with previous findings. Conclusion: The results from this real-world analysis confirm CPX-351 as an efficient treatment for these high-risk AML patients bridging to facilitating allo-HCT in many patients with encouraging outcome after transplantation. Disclosures Röllig: AbbVie: Honoraria, Research Funding; Amgen: Honoraria; Bristol-Meyer-Squibb: Honoraria, Research Funding; Janssen: Honoraria; Jazz: Honoraria; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Honoraria, Research Funding. Stelljes: Pfizer: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau. Gaidzik: Janssen: Speakers Bureau; Pfizer: Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Unglaub: Novartis: Consultancy, Other: travel costs/ conference fee; JazzPharma: Consultancy, Other: travel costs/ conference fee. Thol: Abbvie: Honoraria; Astellas: Honoraria; BMS/Celgene: Honoraria, Research Funding; Jazz: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Krause: Siemens: Research Funding; Takeda: Honoraria; Pfizer: Honoraria; art-tempi: Honoraria; Kosmas: Honoraria; Gilead: Other: travel support; Abbvie: Other: travel support. Haenel: Celgene: Consultancy, Honoraria; Amgen: Consultancy; Novartis: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Bayer Vital: Honoraria; Jazz: Consultancy, Honoraria; GSK: Consultancy. Vucinic: Novartis: Honoraria; Janssen: Honoraria, Other: Travel Sponsoring; Abbvie: Honoraria, Other: Travel Sponsoring; Gilead: Honoraria, Other: Travel Sponsoring; MSD: Honoraria. Fransecky: Novartis: Honoraria; Medac: Honoraria; Abbvie: Honoraria, Research Funding; Amgen: Honoraria; Takeda: Honoraria. Holtick: Celgene: Honoraria; Sanofi: Honoraria. Kobbe: Celgene: Research Funding. Holderried: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Speakers Bureau; Gilead Sciences: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; MSD: Speakers Bureau; Daiichi Sankyo: Other: travel support; Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Therakos: Other: Travel support; Janssen: Other: Travel support; Abbvie: Other: Travel support; Eurocept Pharmaceuticals: Other: Travel support; Medac: Other: Travel support. Heuser: Astellas: Research Funding; Bayer AG: Honoraria, Research Funding; BMS/Celgene: Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; BergenBio: Research Funding; Daichi Sankyo: Honoraria, Research Funding; Karyopharm: Research Funding; Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Research Funding; Tolremo: Honoraria; AbbVie: Honoraria; Janssen: Honoraria. Sauer: Pfizer: Consultancy, Speakers Bureau; Abbvie: Consultancy, Speakers Bureau; Matterhorn Biosciences AG: Consultancy, Other: DSMB/SAB Member; Takeda: Consultancy, Other: DSMB/SAB Member. Goetze: Abbvie: Other: Advisory Board; BMS/Celgene: Other: Advisory Board, Research Funding. Döhner: Jazz Roche: Consultancy, Honoraria; Agios and Astex: Research Funding; Astellas: Research Funding; Abbvie: Consultancy, Honoraria; Janssen: Honoraria, Other: Advisory Board; Daiichi Sankyo: Honoraria, Other: Advisory Board; Novartis: Consultancy, Honoraria, Research Funding; Celgene/BMS: Consultancy, Honoraria, Research Funding. Döhner: Jazz Pharmaceuticals: Honoraria, Research Funding; Agios: Honoraria, Research Funding; Pfizer: Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Gilead: Honoraria; Janssen: Honoraria; Helsinn: Honoraria; GEMoaB: Honoraria; Amgen: Honoraria, Research Funding; Astellas: Honoraria, Research Funding; Astex Pharmaceuticals: Honoraria; AstraZeneca: Honoraria; Berlin-Chemie: Honoraria; Oxford Biomedica: Honoraria; Roche: Honoraria. Schliemann: Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Other: travel grants; Astellas: Consultancy; AstraZeneca: Consultancy; Boehringer-Ingelheim: Research Funding; BMS: Consultancy, Other: travel grants; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Schetelig: Roche: Honoraria, Other: lecture fees; Novartis: Honoraria, Other: lecture fees; BMS: Honoraria, Other: lecture fees; Abbvie: Honoraria, Other: lecture fees; AstraZeneca: Honoraria, Other: lecture fees; Gilead: Honoraria, Other: lecture fees; Janssen: Honoraria, Other: lecture fees . Germing: Novartis: Honoraria, Research Funding; Janssen: Honoraria; Bristol-Myers Squibb: Honoraria, Other: advisory activity, Research Funding; Celgene: Honoraria; Jazz Pharmaceuticals: Honoraria. Schroeder: JAZZ: Honoraria, Research Funding.

Abstract: Background Chronic myeloid leukemia (CML)-study IV was designed to explore whether treatment with imatinib (IM) at 400mg/day (n=400) could be optimized by doubling the dose (n=420), adding IFN (n=430) or cytarabine (n=158) or using IM after IFN-failure (n=128). Methods From July 2002 to March 2012, 1551 newly diagnosed patients in chronic phase were randomized into a 5-arm study. The study was powered to detect a survival difference of 5% at 5 years. The impact of patients' and disease factors on survival was prospectively analyzed. At the time of evaluation, at least 62% of patients still received imatinib, 26.2% were switched to 2nd generation tyrosine kinase inhibitors. Results After a median observation time of 9.5 years, 10-year overall survival was 82%, 10-year progression-free survival 80% and 10-year relative survival 92%. In spite of a faster response with IM800mg, the survival difference between IM400mg and IM800mg was only 3% at 5 years. In a multivariate analysis, the influence on survival of risk-group, major-route chromosomal aberrations, comorbidities, smoking and treatment center (academic vs. other) was significant in contrast to any form of initial treatment optimization. Patients that reached the response milestones 3, 6 and 12 months, had a significant survival advantage of about 6% after 10 years regardless of therapy. The progression probability to blast crisis was 5.8%. Blast crisis was proceeded by high-risk additional chromosomal aberrations. Conclusions For responders, monotherapy with IM400mg provides a close to normal life expectancy independent of the time to response. Survival is more determined by patients' and disease factors than by initial treatment selection. Although improvements are also needed for refractory disease and blast crisis, more life-time can currently be gained by carefully addressing non-CML determinants of survival. Disclosures Hehlmann: Novartis: Research Funding; BMS: Consultancy. Saussele: Pfizer: Honoraria; Incyte: Honoraria; Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding. Pfirrmann: BMS: Honoraria; Novartis: Honoraria. Krause: Novartis: Honoraria. Baerlocher: Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria. Bruemmendorf: Novartis: Research Funding. Müller: Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Ariad: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding. Jeromin: MLL Munich Leukemia Laboratory: Employment. Hänel: Roche: Honoraria; Novartis: Honoraria. Burchert: BMS: Honoraria. Waller: Mylan: Consultancy, Honoraria. Mayer: Eisai: Research Funding; Novartis: Research Funding. Link: Novartis: Honoraria. Scheid: Novartis: Honoraria. Schafhausen: Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria; Ariad: Honoraria. Hochhaus: Incyte: Research Funding; MSD: Research Funding; Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; ARIAD: Research Funding.

Abstract: 7051 Background: Since complete molecular remission (CMR 4.5) defines a subgroup of patients who may stay in remission even after discontinuation of treatment, we analysed whether CMR 4.5 is reached faster with dose optimized IM 800 mg and whether the achievement of CMR 4.5 at specified points in time results in better survival than the achievement of less deep remissions. Methods: Confirmed CMR 4 and CMR 4.5 are defined as ≤ 0.01% BCR-ABL IS or ≥ 4 log reduction and ≤ 0.0032% BCR-ABL IS or ≥ 4.5 log reduction, respectively, from standardized baseline as determined by real-time PCR in 2 independent analyses. Details on CML-Study IV have been published (Hehlmann et al., JCO 2011). Cumulative incidences were estimated under consideration of competing risks. Landmark analyses were performed to evaluate the prognostic impact of different remissions at 4 years on survival. Results: Of 1551 randomized patients with newly diagnosed chronic phase CML 1525 were evaluable. Median age was 52 years, 88% were EUTOS low risk, 12% high risk. 113 patients were transplanted (73 in first chronic phase), 246 received 2nd generation TKI. 152 patients have died. After a median observation time of 67.5 months, 6-year OS was 88.2%.CMR 4.5 was reached after a median of about 76.1 months with IM 800 and 107.3 months with IM 400. EUTOS low-risk patients reached all remissions faster than high-risk patients. Independent of treatment approach CMR 4.5 at 4 years predicted OS significantly better than complete cytogenetic remission (p=0.043), but not significantly better than major molecular remission (MMR) or CMR4. After a median observation of 3.9 years 1 of 626 patients with CMR 4 has progressed. Only six of the 394 patients with CMR 4.5 have died after a median observation time of 3.0 years, no patient has progressed. An additional finding was that achieving MMR at 3 and at 6 months predicts faster achievement of CMR 4.5. Conclusions: We conclude that dose optimized IM 800 induces CMR 4.5 faster than IM 400 and that CMR 4.5 at 4 years is associated with a survival advantage. Dose optimized IM 800 may provide an improved therapeutic basis for treatment discontinuation in patients with CML. Clinical trial information: NCT00055874.

Abstract: Deep molecular response (MR 4.5 ) defines a subgroup of patients with chronic myeloid leukemia (CML) who may stay in unmaintained remission after treatment discontinuation. It is unclear how many patients achieve MR 4.5 under different treatment modalities and whether MR 4.5 predicts survival. Patients and Methods Patients from the randomized CML-Study IV were analyzed for confirmed MR 4.5 which was defined as ≥ 4.5 log reduction of BCR-ABL on the international scale (IS) and determined by reverse transcriptase polymerase chain reaction in two consecutive analyses. Landmark analyses were performed to assess the impact of MR 4.5 on survival. Results Of 1,551 randomly assigned patients, 1,524 were assessable. After a median observation time of 67.5 months, 5-year overall survival (OS) was 90%, 5-year progression-free-survival was 87.5%, and 8-year OS was 86%. The cumulative incidence of MR 4.5 after 9 years was 70% (median, 4.9 years); confirmed MR 4.5 was 54%. MR 4.5 was reached more quickly with optimized high-dose imatinib than with imatinib 400 mg/day (P = .016). Independent of treatment approach, confirmed MR 4.5 at 4 years predicted significantly higher survival probabilities than 0.1% to 1% IS, which corresponds to complete cytogenetic remission (8-year OS, 92% v 83%; P = .047). High-dose imatinib and early major molecular remission predicted MR 4.5 . No patient with confirmed MR 4.5 has experienced progression. Conclusion MR 4.5 is a new molecular predictor of long-term outcome, is reached by a majority of patients treated with imatinib, and is achieved more quickly with optimized high-dose imatinib, which may provide an improved therapeutic basis for treatment discontinuation in CML.

Abstract: Abstract 3411 Background: Dose of therapy and time to response may be different in the elderly as compared to younger patients with CML. This has been reported previously for interferon α (Berger et al., Leukemia 2003). For imatinib, contradictory results have been presented (Rosti et al. Haematologica 2007, Guliotta et al. Blood 2009). Aims: An analysis comparing dose-response relationship in patients more or less than 65 years (y) of age is warranted. Methods: We analysed the German CML-Study IV, a randomized 5-arm trial to optimize imatinib therapy by combination, dose escalation and transplantation. Patients older and younger than 65y randomized to imatinib 400 mg (IM400) or 800 mg (IM800) were compared with regard to time to hematologic, cytogenetic and molecular remissions, imatinib dose, adverse events (AEs) and overall survival (OS). Results: From July 2002 to April 2009, 1311 patients with Ph+ CML in chronic phase were randomized, 623 patients were evaluable, 311 patients for treatment with IM400 and 312 for IM800. 84 (27%) and 66 (21%), respectively, were older than 65 years. All patients were evaluable for hematologic, 578 (140 〉 65y and 438 〈 65y) for cytogenetic, and 600 (143 and 457, respectively) for molecular responses. Median age was 70y vs. 49y for IM400 and 69y vs. 46y for IM800. The median dose per day was lower for elderly patients with IM800 (517mg vs. 666mg) and the same with IM400 (400mg each). Patients' characteristics at baseline were evenly distributed in all groups regarding gender, follow-up, hemoglobin, platelet count and spleen size. Leukocyte counts were significantly lower in elderly patients (IM400: 50/nl vs. 78/nl, IM800: 36/nl vs. 94/nl). EURO score was different due to age in elderly patients (low risk: IM400: 11% vs. 43%, IM800: 14% vs. 42%; intermediate risk: IM400: 79% vs. 44% and IM800: 73% and 43%). There was no difference in cytogenetic and molecular analyses between treatment groups. With regard to efficacy, there was no difference for older patients in achieving a complete cytogenetic remission (CCR) and major molecular remission (MMR) if IM400 and IM800 were compared together. If treatment groups were analyzed separately, older patients treated with IM400 reached CCR and MMR statistically significant slower than younger patients (CCR: median 14.2 months vs. 12.1 months, p=0.019; MMR: median 18.7 months vs. 17.5 months, p=0.006). There was no difference with IM800 (CCR: median 7.7 months vs. 8.9 months, MMR: median 9.9 months vs. 10.0 months). 3y-OS for older patients 〉 65y was 94.7% and for patients 〈 65y was 96.1%. Some differences were observed in the safety analyses. 530 patients (IM400: 278, IM800: 252) were evaluated on common toxicity criteria (WHO). Some hematologic AEs were documented slightly more often in the elderly than in the younger patients: for IM400 anemia grade 1–2 (60 vs. 42%) and leukopenia grade 3–4 (5.6 vs. 1.4%) and for IM800 anemia grade 1–4 (64 vs.47% and 7.2 vs. 5.7%) and thrombocytopenia grade 3–4 (9.3 vs. 7.1%). Non hematologic AEs were more prominent in IM800 and were mainly gastrointestinal symptoms (IM400: 33 vs. 31%, IM800: 48 and 44%) and edema (IM400: 28 vs. 29%, IM800: 35 vs. 50%). There was no difference for grade 3/4 non-hematological AEs in older patients in both groups. Conclusions: Imatinib 400 mg and 800 mg are well tolerated also in the elderly. The IM800 dosage was more tolerability-adapted for the elderly, but there was no difference in reaching a CCR and MMR in contrast to the IM400 where a significantly slower response was detected in the elderly. Whether this difference is clinically relevant has yet to be determined. Updated results will be presented. Disclosures: Haferlach: MLL Munich Leukemia Laboratory: Employment, Equity Ownership, Research Funding. German CML-Study Group:Deutsche Krebshilfe: Research Funding; Novartis: Research Funding; Roche: Research Funding; BMBF: Research Funding; Essex: Research Funding.

Abstract: Depth of molecular remission on tyrosine kinase inhibitor (TKI) treatment is of rising importance for chronic myeloid leukemia (CML) patients (pts) with regard to possible treatment discontinuation and competing TKIs available to improve molecular response. At present, it is unknown which level of deep molecular response is necessary for optimal prognosis and for successfully stopping therapy. The aim of this work is both to evaluate the technical feasibility of molecular monitoring at the mentioned level and to search for factors allowing to predict MR5.0 in pts on imatinib (IM)-based treatment. Methods Real-time quantitative PCR on mRNA BCR-ABL transcripts in addition to total ABL transcripts as internal control has been performed on a LightCycler platform in 1,442 pts within the randomized CML-Study IV and adapted according to the International Scale (IS). In order to qualify for MR5.0 the BCR-ABLIS expression should meet one of the following criteria: a positive result ≤0.001% or a negative result with a minimum sample quality of 100,000 ABL copies (Cross et al., Leukemia 2012). Calculating cumulative incidences of remission or progression, the competing risks progression and/or death before possible progression were considered. Cox models were estimated for the multivariate analysis. Results In 1,198 of the 1,442 molecularly examined pts at least one sample fulfilled the sensitivity criteria for a MR5.0 (8,266 of 24,101 samples, 34.3%). Cumulative incidence of MR5.0 was 51% at 8 years. The median time to MR5.0 according to randomized treatment arms differed as follows: IM 800mg 79.7 months (mos), IM 400mg 95.0 mos, IM 400mg + IFNα 98.0 mos, IM 400mg + AraC 103.3 mos, IM 400mg after IFN failure 112.9 mos. A Cox model examining the different treatment arms compared to IM 400mg revealed a significantly higher chance for MR5.0 in the IM 800mg arm (HR 1.305, 95% CI 1.003-1.698, p=0.048). Baseline factors like thrombocytosis 〉 450/nl were associated with better responses (HR 1.701 compared to 〈 450/nl, 95% CI 1.405-2.059, p 〈 0.001) and higher leukocyte counts 〉 100/nl (HR 0.503 compared to 〈 50/nl, 95% CI 0.400-0.632, p 〈 0.001) and 50-100/nl (HR 0.746 compared to 〈 50/nl, 95% CI 0.591-0.942, p=0.014) with unfavorable responses. Other upfront factors like age, gender, blasts, eosinophils, hemoglobin, and EUTOS score did not significantly influence the probability for MR5.0. Taken all treatment arms together, our analyses have shown that the chance of achieving a MR5.0 by 8 years was considerably reduced if the pts had a BCR-ABLIS 〉 10% at 3 mos (40.2% vs 58.0%), 〉 1% at 6 mos (40.3% vs 68.7%), 〉 0.1% at 12 mos (37.7% vs 72.0%), and 〉 0.1% at 24 mos (21.5% vs 60.5%). Conclusion This evaluation of a large randomized trial reveals feasibility of MR5.0 detection in the majority of pts underlining the benefits of standardized molecular monitoring on the IS with optimized highly sensitive technologies. Baseline low leukocyte count, high thrombocyte count and high dose IM treatment are predictors of future MR5.0. Further, early molecular landmarks qualify for excellent outcome giving hope to a rising number of pts to successfully discontinue treatment and avoid possible side effects or comorbidities. Disclosures: Müller: Novartis: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Ariad: Consultancy, Honoraria, Research Funding. Hehlmann:BMS: Consultancy, Research Funding; Novartis: Research Funding. Hochhaus:Novartis: Consultancy, Honoraria, Research Funding, Travel Other; BMS: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Ariad: Consultancy, Honoraria. Saussele:Novartis: Honoraria, Research Funding, Travel Other; BMS: Honoraria, Research Funding, Travel, Travel Other; Pfizer: Honoraria.

Abstract: Current evidence indicates that acquired genetic instability in chronic myeloid leukemia (CML) as a consequence of the balanced reciprocal translocation t(9;22)(q34;q11) or the variant translocation t(v;22) and the resulting BCR-ABL fusion causes the continuous acquisition of additional chromosomal aberrations (ACA) and mutations and thereby progression to accelerated phase and blast crisis (BC). At least 10% of patients in chronic phase (CP) CML show ACA already at diagnosis and more than 80% of patients acquire ACA during the transformation process into BC. Therefore, alterations at diagnosis as well as acquisition of chromosomal changes during treatment are considered as a poor prognostic factor. Differences in progression-free survival (PFS) and overall survival (OS) have been detected depending on the type of ACA. Patients with major route ACA (+8, i(17)(q10), +19, +der(22)t(9;22)(q34;q11)) and with other alterations like -X, del(1)(q21), del(5)(q11q14), +10, -21 at diagnosis resulting in an unbalanced karyotype have a worse outcome. Patients with minor route ACA (for example reciprocal translocations other than the t(9;22)(q34;q11) (e.g. t(1;21), t(2;16), t(3;12), t(4;6), t(5;8), t(15;20)) resulting in a balanced karyotype show no differences in OS and PFS compared to patients with the standard translocation, a variant translocation or the loss of the Y chromosome (Fabarius et al., Blood 2011). Here we compare the type of chromosomal changes (i.e. balanced vs. unbalanced karyotypes) during the course of the disease from CP to BC aiming to provide a valid parameter for future risk stratification. Patients and Methods Clinical and cytogenetic data available from 1,346 out of 1,524 patients at diagnosis (40% females vs. 60% males; median age 53 years (range, 16-88)) with Philadelphia and BCR-ABL positive CP CML included until March 2012 in the German CML-Study IV (a randomized 5-arm trial to optimize imatinib therapy) were investigated. ACA were comparatively analyzed in CP and in BC. Results At diagnosis 1,174/1,346 patients (87%) had the standard t(9;22)(q34;q11) only and 75 patients (6%) had a variant t(v;22). Ninety-seven patients (7%) had additional cytogenetic aberrations. Of these, 44 patients (3%) lacked the Y chromosome (-Y) and 53 patients (4%) had ACA. Regarding the patients with ACA thirty-six of the 53 patients (68%) had an unbalanced karyotype and 17/53 patients (32%) a balanced karyotype. During the course of the disease 73 patients (out of 1,524 patients) developed a BC during the observation time (5%). Cytogenetic data were available in 52 patients with BC (21 patients with BC had no cytogenetic analysis). Three patients had a normal male or female karyotype after stem cell transplantation. Nine patients showed the translocation t(9;22)(q34;q11) or a variant translocation t(v;22) (six and three patients, respectively) only and in 40 patients ACA could be observed in BC (40/49 (82%)). Out of these 40 patients with ACA, 90% showed an unbalanced karyotype whereas only 10% of patients had a balanced karyotype. No male patient in BC showed the loss of the Y chromosome pointing to a minor effect of this numerical alteration on disease progression. Conclusion We conclude that patients with CML and unbalanced karyotype at diagnosis are under higher risk to develop CML BC compared to patients with balanced karyotypes or compared to patients without ACA. In BC, 90% of CML patients showed unbalanced karyotypes (only 68% of CML patients at diagnosis have unbalanced karyotypes) supporting the hypothesis that the imbalance of chromosomal material is a hallmark of disease progression, representing the natural history of the disease from CP to BC and indicating therefore a strong prognostic impact. Consequently, different therapeutic options (such as intensive therapy or stem cell transplantation) should be considered for patients with unbalanced karyotypes in CP CML at diagnosis. Disclosures: Haferlach: MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Hehlmann:BMS: Consultancy, Research Funding; Novartis: Research Funding. Hochhaus:Novartis: Consultancy, Honoraria, Research Funding, travel Other; BMS: Consultancy, Honoraria, Research Funding; Pfizer : Consultancy, Honoraria; Ariad : Consultancy, Honoraria. Müller:Ariad: Honoraria; BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding, Speakers Bureau. Saussele:Pfizer: Honoraria; BMS: Honoraria, Research Funding, Travel, Travel Other; Novartis: Honoraria, Research Funding, Travel Other.