High frequency of extramedullary relapse of acute leukemia after allogeneic bone marrow transplantation

We investigated the frequency and mode of relapses of acute leukemia after allogeneic BMT in a series of 50 consecutive patients. The median age of patients was 31.5 years with 26 males. Thirty-two patients had AML. Forty-three patients were in first CR. All patients received BuCy regimen with GVHD prophylaxis of cyclosporine plus methotrexate. After a median follow-up time of 22.4 months (range, 6.0-52.9), 14 patients (28%) relapsed. Seven patients (50%) relapsed in the bone marrow only; three (21%) relapsed in extramedullary sites only; and four (29%) relapsed in both extramedullary sites and bone marrow. Times to relapses in bone marrow only (median 6.3 months) were significantly shorter when compared to times to extramedullary relapses with or without bone marrow involvement (median 12.3 months, P = 0.048). Sites of extramedullary relapses varied widely among the patients. In conclusion, we observed a high frequency of extramedullary relapses of acute leukemia after allogeneic BMT (50%). The GVL effect observed in the extramedullary sites of the body may not be as effective as in the bone marrow in patients with acute leukemia after allogeneic BMT.