Reduced-intensity conditioning allogeneic stem cell transplantation for multiple myeloma: results from the Japan Myeloma Study Group.

We conducted a retrospective survey of multiple myeloma (MM) patients who underwent reduced-intensity conditioning allogeneic stem cell transplantation (RIST) at 11 hospitals participating in the Japan Myeloma Study Group. Forty-five patients (median age, 53 years) were included in this study. The conditioning regimen consisted of a fludarabine-based regimen in 24 patients and a regimen based on total body irradiation (1-2 Gy) in 18 patients. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and tacrolimus in 28 and 17 patients, respectively. All patients showed myeloid engraftment. Complete chimerism was obtained in 42 patients. Grade II to IV acute GVHD developed in 28 (65%) of 43 patients evaluated, and chronic GVHD developed in 31 (76%) of 41 patients. Early death before day 100 was observed in 4 patients (8.8%). A complete response (CR) was obtained in 12 patients. The factors affecting overall survival were severe acute GVHD and the response after RIST. To date, 18 patients are alive, with 9 patients remaining in CR at a median follow-up of 25 months. The overall and progression-free survival rates at 3 years were 38.5% and 18.8%, respectively. These observations suggest that RIST is feasible with reliable donor engraftment and relatively low transplantation-related mortality in Japanese MM patients.