Aim: The objective of the study was to estimate the cumulative incidence (CI) of relapse, relapse-free survival (RFS) and overall survival (OS) in ALL patients after a once-a-day fractionated TBI (F-TBI) regimen with 9.9Gy. The secondary objectives were evaluation of short and long-term toxicity and non-relapse mortality (NRM). Background: Total body irradiation (TBI), as a part of the conditioning regimen
before allogeneic stem cell transplantation (ASCT) for acute lymphoblastic leukemia (ALL), allows disease control by eradicating residual blast cells in the transplant recipient. Materials and methods: Retrospective study conducted in patients with ALL who received between March 2003 and December 2013 a conditioning regimen with F-TBI and chemotherapy. Irradiation was delivered with 3.3Gy once-a-day for three consecutive days. Results: Eighty-seven patients were included. The median age was 19 years (range: 5-49 years). The 3-year CI of relapse was 30%. The estimated 3-year RFS and OS were 54% and 58%, respectively. Cumulative incidence of acute graft-versus-host disease (aGVHD) grade II-IV and chronic GVHD (cGVHD) was 31% and 40%, respectively. Interstitial pneumonitis was observed in 2 patients. The 3-year CI of NRM was 16%. In multivariate analysis, cGVHD was associated with a lower CI of relapse (RR=0.26, 95% CI: 0.07-0.95, p=0.04). High-risk cytogenetics was associated with a lower RFS (RR=2, 95 CI: 1.04-3.84, p=0.03). Grade II-IV aGVHD was an independent predictor of higher CI of NRM (RR=6.7, 95% CI: 1.4-31.7, p=0.02). Conclusions: Once-a-day F-TBI regimen is effective, safe and practical in patients who underwent ASCT for ALL.