Relapse after non-T-cell-depleted allogeneic bone marrow transplantation for chronic myelogenous leukemia: early transplantation, use of an unrelated donor, and chronic graft-versus-host disease are protective.

We analyzed the incidence of posttransplant chronic myelogenous leukemia (CML) relapse in 283 consecutive related-donor (n = 177) and unrelated-donor (n = 106) allogeneic transplant recipients. Twenty-two of 165 related-donor recipients with stable or advanced disease at the time of transplant had hematologic relapse of CML following transplant (5-year Kaplan-Meier estimate of relapse, 20%; 95% confidence interval [CI], 11 to 30%). One of 12 patients transplanted in second stable phase following blast crisis also relapsed. Fifteen related-donor transplant recipients relapsed within 5 years of transplant; however, seven relapsed between 5 and 9 years after transplant. Factors independently associated with an increased risk of posttransplant relapse for related-donor recipients included prolonged interval between diagnosis and transplant (relative risk, [RR], 3.81; P = .009) and bone marrow basophilia (RR, 5.62; P = .01). Related-donor recipients with posttransplant chronic graft-versus-host disease (CGVHD) had a decreased risk of relapse (RR, 0.24; P = .005). Only two of 106 unrelated-donor transplant recipients relapsed following transplant (5-year Kaplan-Meier estimate of relapse, 3%; 95% CI, 0% to 7%). When both related- and unrelated-donor recipients were considered, the use of an unrelated donor was independently associated with a decreased risk of relapse (RR, 0.24; P = .07). Twelve of 16 relapsing patients who received further therapy (nine of 13 who underwent second transplant and three of three who received donor leukocyte infusions) remain alive. This analysis shows that relapse, sometimes occurring long after transplant, is an important adverse outcome in allogeneic transplantation for CML. Early transplant, posttransplant CGVHD, and use of an unrelated donor are associated with a reduced incidence of relapse, perhaps due to allogeneic disparities enhancing the graft-versus-leukemia effect.