T-Cell Depleted Unrelated Donor Stem Cell Transplants Appear to Be of Value for Adult Philadelphia Chromosome Negative ALL Patients and Should Be Evaluated Prospectively in New Large Group Studies

Abstract

Matched sibling allogeneic haematopoietic stem cell transplantations (HSCT) in first complete remission (CR1) result in superior survival compared to standard chemotherapy in adult patients with acute lymphoblastic leukaemia (ALL). However, application is limited by donor availability. The role of unrelated donor (URD) transplantation in ALL in CR1 is not clearly delineated. We report a retrospective series of URD transplants in 55 adults with Philadelphia chromosome (Ph) negative acute lymphoblastic leukaemia (ALL) in CR1 reported to the British Society of Blood and Marrow Transplantation registry from 1993 to 2005. Median follow-up of survivors was 55.2 months (range 17–160). Median age was 25.5 years (range 15.7–50). Eighty nine percent of patients had at least one adverse prognostic feature. Sixty six percent of transplants were matched at 10 of 10 loci and 34% were mis-matched. T cell depletion (TCD) was carried out by in-vivo Campath administration in 96% of recipients with additional ex-vivo TCD in 21% of these patients. The estimated actuarial Overall survival (OS), Disease free survival (DFS) and non relapse mortality (NRM) were 59%, 57% and 19% at 5 years respectively. The overall incidence of Grade II–IV and III–IV GVHD was 25% and 7% respectively. The actuarial estimate of extensive chronic GVHD was 22 % at 5 years. HLA mismatching at 2 alleles or antigens was associated with poorer survival (RR=3.22, (1.08–9.64). T depleted URD HSCT can result in good OS and low TRM for adults with high risk ALL in CR1 and merits prospective comparison with other methods of GVHD prophylaxis.