Safe application of a 13-Gy split dose total body irradiation schedule prior to bone marrow transplantation.

Two conditioning regimens for bone marrow transplantation for patients with acute lymphoblastic leukaemia were compared. Both regimens (VVRAPID and VVRAPID-X) incorporated the same cytotoxic chemotherapy but differed in the radiation dose; VVRAPID employed a single fraction of 10.5 Gy and VVRAPID-X employed 10.5 Gy followed 4 days later by a further dose of 2.5 Gy. The 13-Gy split-fraction schedule was well tolerated with no significant increase in infection or requirement for blood products. An increase in gastrointestinal toxicity occurred but responded to increased oral anti-diarrhoeal agents. Overall survival and relapse rates did not differ significantly between the two groups. There was a trend for the 13-Gy schedule to reduce the graft failure rate following T cell-depleted bone marrow transplants.