Tandem Autologous Hematopoietic Stem Cell Transplants (AuHCT) with or without Maintenance Therapy (auto-auto) Versus Single AuHCT Followed by HLA Matched Sibling Non- Myeloablative Allogeneic HCT (auto-allo) for Patients with Standard Risk (SR) Multiple Myeloma (MM): Results From the Blood and Marrow Transplant Clinical Trials Network (BMT CTN) 0102 Trial (2010)

Abstract Abstract 41 AuHCT improves survival in patients with MM, but disease relapse and progression remain a challenge. Both tandem AuHCT and post transplant maintenance therapy improve progression-free survival (PFS). Alternatively, allogeneic HCT has the potential to reduce disease progression through a graft-versus-myeloma effect. Use of nonmyeloablative conditioning regimens allows the latter approach to be used with reduced treatment-related mortality (TRM). BMT CTN 0102 was a multicenter phase III trial that biologically assigned patients with MM to auto-auto using melphalan 200mg/m2 (MEL 200) conditioning or an auto-allo approach using MEL 200 followed by alloHCT with 2 Gy total body irradiation. Graft-versus-disease (GVHD) prophylaxis was cyclosporine and mycophenolate mofetil. The primary endpoint was 3-year progression free survival (PFS). Between December 2003 and March 2007, 710 patients from 43 US centers were enrolled. Patients were assigned to the auto-allo arm based on availability of an HLA-matched sibling donor at time of enrollment. Patients in the auto-auto arm were further randomized to thalidomide and dexamethasone (Thal-Dex) for 1 year or observation (obs). Among 625 patients with SR MM (absence of chromosome 13 deletion by metaphase karyotyping and β-2 microglobulin ≤ 4mg/L), 436 were assigned to auto-auto (217 Thal-Dex, 219 obs) and 189 to auto-allo. Compliance with Thal-Dex was poor, with 84% of patients not completing prescribed therapy. PFS and overall survival (OS) between the Thal-Dex and obs cohorts were equal and these arms were pooled for the primary analysis. The auto-auto and auto-allo groups differed in age (median 55y vs. 52y, p =0.01) and time between first and second transplants (median 98d vs 105d, p =0.02), but were otherwise balanced. Complete and near complete (CR+nCR) response rates at study entry were 24% for both groups. Three-year PFS was 46% and 43% (p=0.67) and 3-year OS was 80% and 77 % (p=0.19) for the auto-auto and auto-allo groups, respectively. Corresponding probabilities for 3-year progression/relapse were 50% and 46% (p=0.8) and for 3-year TRM were 4% and 11% (p=0.04). Among auto-allo patients, probabilities of grade III-IV acute and chronic GVHD were 9% and 47%, respectively. Eighty-two percent of patients in each arm received the assigned second transplant. Among 522 patients who received their second transplant, 3-year PFS was 47% and 44% (p=0.89) with auto-auto and auto-allo, respectively. Disease response rates at day 56 after second HCT were: 50% very good partial response (VGPR) or better and 40% CR+nCR in the auto-auto group; and 49% (VGPR or better, p=0.8) and 48% (CR+nCR,p=0.12) in the auto-allo group. In conclusion, there were no differences in 3-year PFS and OS between patients receiving auto-auto or auto-allo. Potential benefits of graft-versus-myeloma to reduce disease progression or relapse were offset by increased TRM. Thal-Dex maintenance did not improve PFS or OS, likely due to poor tolerability of this regimen. At 3 years, the auto-allo approach for SR MM had no added benefit compared to tandem AuHCT. Disclosures: Krishnan: Celgene: Speakers Bureau. Stadtmauer:Celgene: Speakers Bureau. Comenzo:Millenium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Elan Pharmaceuticals: Consultancy; Genzyme: Research Funding; Celgene: Research Funding; Ortho: Research Funding. Hari:Celgene: Research Funding. Qazilbash:Celgene: Speakers Bureau. Vesole:Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Giralt:Celgene: Honoraria, Speakers Bureau; Millenium: Honoraria, Speakers Bureau.