Fractionated total body irradiation in marrow transplantation for leukaemia

Thirty consecutive patients with leukaemia were prepared for bone marrow transplantation (BMT) with cyclophosphamide (CY) 120 mg/kg followed by total body irradiation (TBI). TBI was delivered in a single dose (sTBI) of 10 Gy, at a dose rate of 0.06-0.08 Gy/min, or in fractionated doses (fTBI) of 3.3 Gy/d, on each of 3 consecutive days, at the same dose rate. Lung shielding was adopted for all patients, in order to obtain a homogeneous dose delivered to the lung and at midline. The first 12 patients were prepared with sTBI and the following 18 with fTBI. Several variables (remission status, mode of irradiation, prevention of graft versus host disease (GvHD) with methotrexate (MTX) or cyclosporin A(CyA) were then analysed for their influence on (a) incidence and mortality of GvHD, (b) incidence and mortality of interstitial pneumonia (IP), (c) 100-d survival, and (d) relapses. Our data suggest that fTBI is the single most important factor associated with a lower incidence of IP (P = 0.002), a lower mortality from GvHD and IP (P = 0.03 and 0.001) and a better 100-d survival (P = 0.03). Remission status had no significant influence on GvHD, IP and acute mortality. When compared to MTX, the use of CyA was associated with less GvHD and IP, but when only patients in remission given fTBI were analysed, this was no longer true. Relapses were mostly influenced by the remission status of the patient at transplant (P = 0.001). Although this is not a randomized study, our data suggest that fTBI can reduce the acute risks of marrow transplantation in leukaemia.