Autologous bone marrow transplantation for high risk acute lymphoblastic leukemia: clinical relevance of ex vivo bone marrow purging with monoclonal antibodies and complement

Herein we describe our experience with 75 consecutive autologous BM transpl ants for patients with high-risk ALL, with special attention to the clinica l impact of BM purging. Fifty-two patients received purged BM using monoclo nal antibody (MoAb) cocktails and complement, and 23 patients received untr eated BM. The distribution of prognostic factors was similar in both groups . Hemopoietic reconstitution was adequate and did not differ in the two gro ups. Transplant-related mortality was 9.6% and 13% in 'purged' and 'unpurge d' groups. Median follow up was 11 months (2-71) and overall actuarial prob ability of disease-free survival (DFS) at 5 years was 40% (53% relapse prob ability). We found a beneficial effect of purging in patients over 15 years of age and in patients needing more than 1 month to reach CR1, Patients in CRI receiving purged marrow had a longer DFS and a lower relapse probabili ty (52% vs 12%, P=0.02 and 35% vs 86%, P = 0.005, respectively) which were related to the efficacy of the purging procedure (more or less than one log of depletion). In further CR, no advantage of purging has been found. Our data strongly suggest the clinical relevance of BM purging in autologous BM T in high-risk ALL patients and support the need for prospective randomized studies.