Allogeneic Stem Cell Transplant Versus Tandem High-Dose Melphalan for Front-Line Treatment of Deletion 13q14 Myeloma – An Interim Analysis of the German DSMM V Trial.

Abstract Abstract 51 Background Allogeneic stem cell transplantation (allo SCT), a treatment modality based on transfer of immunocompetent donor lymphocytes offers curative potential to subjects with a variety of hematological cancers. In multiple myeloma (MM), high-dose melphalan followed by autologous stem cell transplantation (auto SCT) is adopted as a standard of care. However, it remains palliative since virtually all patients (pts) relapse and renders allo SCT an option of interest. Deletion of chromosome 13q14 (13q-) in MM has been shown to negatively impact prognosis. Therefore, improvement of therapy for 13q- pts is highly desirable. Patients and methods A prospective two-arm multi-center trial (DSMM V) was set up by our group to compare tandem high-dose melphalan 200 mg/m2 (HD Mel) with a reduced intensity conditioning allo-SCT after one cycle of HD Mel for 13q- MM. Eligibility criteria were 13q- on bone marrow FISH analysis; age up to 60 years; newly diagnosed MM in Salmon and Durie stages II and III; and measurable disease. Allocation to either treatment arm was by availability of an HLA-matched (one mismatch allowed) volunteer related (VRD) or unrelated donor (VUD). Initially, all pts received four cycles of anthracycline/dexamethasone-based induction followed by chemomobilization of peripheral blood stem cells (PBSCT) and one cycle of HD Mel. Allogeneic SCT was performed after preparation with fludarabine (30 mg/m2 for 3 consecutive days) and melphalan 140 mg/m2. ATG was administered for VUD transplants. Results 199 pts with a median age of 53 (range, 30 – 60) years were enrolled between October 2002 and March 2007 and included in this interim analysis. Sixty-seven percent had stage III disease. Allo SCT was performed in 126 of 199 pts (63%), 76 of whom (60%) received VUD allografts. The remaining 73 subjects uniformely received tandem HD Mel. Pts following allo SCT were more likely to achieve CR (59%) when compared to tandem HD Mel (32%; p=.003) within one year after end of therapy. Similarly, overall response rate was significantly higher with allo SCT (91% versus 86%; p=.003). Of note, depth of response to allo SCT was not associated with presence of acute graft-versus-host disease (GVHD): 62% CR with grades II to IV GVHD vs 58% CR with grades 0 and I (p=.75). Treatment-related mortality (TRM) at 2 years from allo SCT was 16/126 (12.7%). At a median follow up of 25 months for tandem HD Mel and 34 months for allo SCT, projected 3-year overall survival is 72% (auto) and 60% (auto/allo SCT; p=0.22), respectively. Conclusions This is the largest trial on first-line allogeneic stem cell transplant in MM so far. Our interim results show a higher CR rate in FISH 13q- subjects undergoing allo SCT when compared to tandem HD Mel. Despite a majority of allografts in our study being delivered from unrelated donors, TRM was comparable to trials confined to sibling transplants. At a relatively short follow-up, there is not yet a difference between both arms regarding OS, albeit longer follow-up may be important as previously described. This as well as analysis of the impact of donor type and chronic GVHD on outcome will be presented at the meeting. Disclosures: No relevant conflicts of interest to declare.