Unrelated donor haematopoietic cell transplantation after non-myeloablative conditioning for patients with high-risk multiple myeloma

Background: Allografting induces long-term molecular remissions and possibly cure in myeloma patients. The development of non-myeloablative conditionings has reduced the transplant-related mortality (TRM) associated with myeloablation and extended the eligible age for transplantation. Moreover, high response rates are reported especially when allografting is preceded by cytoreductive high-dose chemotherapy. We investigated the feasibility of unrelated donor non-myeloablative transplantation as either part of the initial treatment plan or as salvage treatment in heavily pretreated patients. Methods: Twenty-two patients underwent non-myeloablative allografting, 10 as part of their initial treatment and 12 at relapse. Donors were matched for HLA-A, B, C, DRB1 and DQB1 by high-resolution typing. Only one single class I allele disparity was allowed. Conditioning consisted of fludarabine 90 mg/m2 and 2 Gy total body irradiation. Graft-vs.-host disease (GVHD) prophylaxis included cyclosporin and mycophenolate mofetil. Results: All patients except two (91%) readily engrafted. After a median follow-up of 20 (10-30) months, incidences of grade II-IV acute and extensive chronic GVHD were 50% and 61%. Overall response (OR) was 55%, with four (20%) complete and seven (35%) partial remissions. However, in patients allografted up-front OR was 89% whereas in the heavily pretreated group OR was 27% (P = 0.01). Two-year overall and event-free survivals were both 79% in the group transplanted up-front and 27% and 25% among relapsed patients (P = 0.025 and P = 0.006, respectively). Overall, six patients died of TRM and three of disease progression. Conclusions: Unrelated donor non-myeloablative allografting is feasible in myeloma. Disease control appears more pronounced when patients are treated soon after diagnosis.