The benefit of reduced intensity conditioning (RIC) allogeneic stem cell transplantation (allo-SCT) as salvage treatment for relapsing multiple myeloma (MM)

Abstract

8045 Background: The role of RIC allo-SCT in MM is still controversial. This single centre study aimed to evaluate RIC allo- SCT for relapsed MM, using a genetic randomization through a donor vs. no donor comparison. Methods: Between 2002 and 2005, 32 patients with relapsed or refractory MM, and with an identified sibling, were referred to our centre for HLA typing. In all, 19 patients (59%; donor group) had an HLA-identical sibling donor, while the remaining 13 pts (41%; no donor group) had no HLA-identical sibling donor. There were no significant differences between these two groups that were comparable as for demographic, disease and prognosis factors. All pts had previously failed auto-SCT. Results: Among the 19 pts from the donor group, 18 (95%) could proceed to allo-SCT. With a median overall FU of 36 m., 11 patients (85%; 95%CI: 54–98%) from the no donor group had disease progression despite salvage therapy, and only 6 of them are still alive, of whom 5 (80%) in progressive disease at last FU. In contrast, only 5 pts (28%;P=0.001) from the donor group progressed after RIC allo-SCT. In the RIC allo-SCT group, 10 pts (56%;95%CI;33–79%) are still alive, with 4 pts being in CR, and 5 in PR or VGPR. Only one patient is currently experiencing disease progression and receiving salvage therapy. Interestingly, 11 pts (61%;95%CI,39–83%) from the RIC allo-SCT group showed objective disease response, usually concurrent to chronic GVHD. In all, 6 pts died from TRM for an overall incidence of TRM of 33% (95%CI,11–55%) in this population of heavily pretreated and relapsed or refractory MM population. In an intention-to- treat analysis, the KM estimate of progression-free survival was significantly higher in the donor group as compared to the no donor group (P=0.01; 46% vs. 8% at 3 y.). Conclusions: RIC allo-SCT from an HLA-identical sibling is a feasible and potential therapy that should be proposed for refractory or relapsed MM, since a potent graft-vs. -MM effect can be induced despite heavy pretreatments, allowing for significantly longer PFS. Also, the latter results are expected to be further improved with the systematic and early use of maintenance therapies after RIC allo-SCT. No significant financial relationships to disclose.