e282 survival (OS) and progression-free survival (PFS) were 69% (95% CI:6-55%) and 35% (95% CI:6-22%), respectively (Figure 1). On multivariate analysis, chemorefractory disease at alloHCT was associated with an inferior PFS (Hazard risk [HR] 5.75 [95% CI:2.32-14.23]), inferior OS (HR 5.19 [95% CI:2.05-13.14]), higher toxicity related mortality (TRM, HR 6.60 [95% CI: 1.1139.02]) and higher RI/POD (HR 4.04 [95% CI: 1.07-15.21]). Being younger than 55 years emerged as a protective factor for both PFS (HR0.29 [95%CI:0.14-0.60]) and OS (HR 0.29[0.01-0.10]). Chronic GVHD conveyed a higher TRM (HR 1.15 [95%CI:1.021.30]) but not a reduced RI/POD. Conclusion: Our retrospective data show that RIC alloHCT is a safe and effective therapeutic option in MM patients, allowing long survival outcomes even in heavily pretreated patients. Figure 1 OS (A) and PFS (B) of the whole study population 15th International Myeloma Workshop, September 23-26, 2015 PO-349 Durable Remission and Survival in Relapsed/Refractory Multiple Myeloma After Allogeneic Hematopoietic Stem Cell Transplantation A.M. Cornelison, R.M. Saliba, S. Ahmed, Y. Nieto, Q. Bashir, N. Shah, S. Parmar, K. Patel, C. Hosing, U. Popat, E. Shpall, R. Champlin, M.H. Qazilbash Stem Cell Transplantation and Cellular Therapy, University of Texas MD Anderson Cancer Center, Houston, Texas Background: The role of allogeneic hematopoietic stem cell transplantation (allo-HCT) in the setting of refractory multiple myeloma (MM) is still controversial. Although potentially curative in a subset of pts, 10-15% treatment related mortality (TRM) and chronic graft vs. host disease (cGVHD) preclude its universal use. In this study, we evaluated the role of allo-HCT for pts with relapsed MM. Methods: We identified 110 consecutive pts with relapsed MM who underwent allo-HCT at our institution between 2000 and 2014. The primary objective was to assess progression-free (PFS) and overall survival (OS). Results: Median age at allo-HCT was 54 (range, 32-71) years and median time from diagnosis to alloHCT was 35.7 (range, 8.6 to 228.8) months. Fifty-two (47%) and 49 (45%) pts had standard-risk (SR) and high-risk (HR) cytogenetics (CG) at the time of allo-HCT, respectively. Pts received a median of 5 (range, 1-9) prior chemotherapy regimens and 99 pts (90%) had at least 1 (range, 0-3) prior auto-HCTs. One hundred one(92%) pts received either a proteasome inhibitor (PI) or an immunomodulatory drug (IMiD) prior to allo-HCT, with 65 (59%) receiving both. Sixty eight (62%) received allo-HCT from a matched related, 34 (31%) from a matched unrelated, 5 (4%) from a cord blood, and 3 (3%) from a mismatched donor. Preparative regimen was fludarabine/melphalan-based in 88 (80%) and fludarabine/busulfan-based in 16 (15%) patients. Median time to neutrophil and platelet engraftment was 12 (range, 8-30) and 13 (range, 0-81) days, respectively. Ten pts died of non-relapse causes within 100 days (100-day TRM: 9%) and 20 (18%) within 1 year. Grade 1-4 acute GVHD was seen in 50 (45%) and cGVHD in 35 (32%) pts, respectively. Eighteen (16%) achieved a CR, 26 (23%) a VGPR and 38 (34%) achieved a PR, with an overall response rate of 73%. With a median follow up of 11.4 months (range 0.3 to 164) in all pts, and 32.7 months (range 3.6 to 164.3) in surviving pts, 1and 2-year PFS were 24% and 16%, respectively. Similarly, 1and 2-year OS were 52% and 32%, respectively. HR CG at allo-HCT and a response <PR after allo-HCT were associated with significantly shorter PFS (p1⁄40.007 and <0.001, respectively) and OS (p1⁄40.01 and <0.001). (Fig 1) Conclusions: Allo-HCT is associated with durable remission and survival in approximately 20% of heavily pretreated patients with relapsed/refractory MM. Patients with HR CG abnormalities and <PR after allo-HCT need more effective approaches.