Prospective evaluation of unrelated donor bone marrow transplantation. The International Marrow Unrelated Search and Transplant (IMUST) Study.

The International Marrow Unrelated Search and Transplant (IMUST) Study has prospectively assessed outcome of unrelated donor BMT (UD-BMT) in comparison with a matched cohort of patients treated by HLA-identical sibling BMT (ID-BMT). We report an interim analysis of the first 165 UD-BMT and 368 ID-BMT. Eighty-two percent of UD-BMT pairs were matched by serology for HLA-A, B and DR, 10% were less well matched and HLA matching data was incomplete in 8%. The Kaplan-Meier estimated probability of survival until day 400 was 0.42 (95% confidence limits 0.33-0.51) after UD-BMT and 0.62 (0.56-0.68) after ID-BMT (p = < 0.001). Probability of engraftment by day 100 was 0.90 (0.85-0.95) and 0.95-0.99) after UD-BMT and ID-BMT, respectively (p = < 0.001). Cumulative probability of acute GVHD by day 100 was 0.52 (0.45-0.60) and 0.42 (0.37-0.47) after UD-BMT and ID-BMT, respectively (p = 0.009). After UD-BMT, 52% of patients with early disease survived until day 400 (40-64%) and 27% (14-40%) with advanced disease (p = < 0.001). Multifactorial analysis of survival showed success was related to the centre's experience of UD-BMT and this effect was modified by conditioning protocol. Increased probability of survival after UD-BMT in centres with most experience of the procedure is novel finding. We conclude UD-BMT is a more difficult procedure than ID-BMT but results are acceptable in patients with early disease and when UD-BMT is carried out in experienced centres.