Purpose: To investigate whether different procedure variables involved in the delivery of fractionated total body irradiation (TBI) impact on prognosis of patients affected by acute lymphoblastic leukemia (ALL) receiving allogeneic bone marrow transplant (BMT).
Methods and materials: Ninety-three consecutive patients with ALL receiving a human leukocyte antigen (HLA) identical allogeneic BMT between 1 August 1983 and 30 September 1995 were conditioned with the same protocol consisting of cyclophosphamide and fractionated TBI. The planned total dose of TBI was 12 Gy (2 Gy, twice a day for 3 days). Along the 12-year period, variations in delivering TBI schedule occurred with regard to used radiation source, instantaneous dose rate, technical setting, and actual total dose received by the patient. We tested these different TBI variables as well as factors related to patient, state of disease, and transplant-induced disease to investigate their influence on transplant-related mortality, leukemia relapse, and survival.
Results: At median follow-up of 7 years (range 3-15 years) the probabilities of leukemia-free survival (LFS) and overall survival (OS) for the 93 patients were 60% and 41%, respectively. At univariate analysis, chronic graft versus host disease (cGvHd) (p = 0.0005), age (p = 0.01), and state of disease (p = 0.03) were factors affecting LFS whereas chronic GvHd (p = 0.0005), acute GvHd (p = 0.03), age (p = 0.0001), and GvHd prophylaxis (p = 0.01) were factors affecting overall survival. The occurrence of chronic GvHd was correlated with actually delivered TBI dose (p = 0.04). Combined stratification of prognostic factors showed that patients who received the planned total dose of TBI (12 Gy) and were affected by chronic GvHd had higher probabilities of LFS (p = 0.01) and OS (p = n.s.) than patients receiving less than 12 Gy and/or without occurrence of chronic GvHd. Moreover, TBI dose had a significant impact on LFS in patients transplanted in first remission (p = 0.05). At multivariate analysis, TBI dose was an independent factor affecting overall survival (p = 0.05) as well as chronic GvHd (p = 0.001) and age (p = 0.04).
Conclusions: This retrospective analysis showed that different variables involved in TBI delivery may influence the occurrence of cGvHd and affect prognosis of patients with ALL receiving allogeneic BMT. The total dose of 12 Gy, administered in six fractions over 3 days, appears to be an effective and low toxic regimen for ALL patients transplanted in first remission.