INFLUENCE OF THE FRACTIONATION OF TOTAL-BODY IRRADIATION ON COMPLICATIONS AND RELAPSE RATE FOR CHRONIC MYELOGENOUS LEUKEMIA

One hundred eighty patients with chronic myelogenous leukemia, who received an unmanipulated marrow graft from an Human Leucocyte Antigen identical sibling donor, were reported to our group (G.E.G.M.O.) by 21 transplant teams. All were grafted after a total body irradiation-cytoxan conditioning regimen. Of these 180 patients, 126 were non-randomly assigned to single dose total body irradiation (STBI group) and, 54 to fractionated total body irradiation (FTBI group). With a median follow-up of 40 months, there is no statistically significant difference in the 5-year survival rate between the two groups (51% for the whole population). In a first step we demonstrate by multivariate analysis that total body irradiation fractionation can dramatically decrease the incidence of interstitial pneumonitis. However, a multivariate analysis of potent risk factors for relapse post-transplant strongly suggests that TBI fractionation is also linked to an increased relapse rate. So, a sparing effect of fractionation for lung tissue could be offset by a less effective leukemic stem cell kill. Those results from a retrospective, non-randomized, multi-institutional study clearly need additional clinical data, ideally from a randomized study.