Helical tomotherapy targeting total bone marrow after total body irradiation for patients with relapsed acute leukemia undergoing an allogeneic stem cell transplant.

BACKGROUND AND
PURPOSE: To report our clinical experience in planning and delivering total marrow irradiation (TMI) after total body irradiation (TBI) in patients with relapsed acute leukemia undergoing an allogeneic stem-cell transplant (SCT).
MATERIALS AND METHODS: Patients received conventional TBI as 2 Gy BID/day for 3 days boosted the next day by TMI (2 Gy in a single fraction) and followed by cyclophosphamide (Cy) 60 mg/kg for 2 days. While TBI was delivered with linear accelerator, TMI was performed with helical tomotherapy (HT).
RESULTS: Fifteen patients were treated from July 2009 till May 2010, ten with acute myeloid leukemia, and five with acute lymphoid leukemia. At the time of radiotherapy eight patients were in relapse and seven in second or third complete remission (CR) after relapse. The donor was a matched sibling in 7 cases and an unrelated donor in 8 cases. Median organ-at-risk dose reduction with TMI ranged from 30% to 65% with the largest reduction (-50%-65%) achieved for brain, larynx, liver, lungs and kidneys. Target areas (bone marrow sites and spleen in selected cases) were irradiated with an optimal conformity and an excellent homogeneity. Follow-up is short ranging from 180 to 510 days (median 310 days). However, tolerance was not different from a conventional TBI-Cy. All patients treated with TBI/TMI reached CR after SCT. Three patients have died (2 for severe GvHD, 1 for infection) and 2 patients showed relapsed leukemia. Twelve patients are alive with ten survivors in clinical remission of disease.
CONCLUSIONS: This study confirms the clinical feasibility of using HT to deliver TMI as selective dose boost modality after TBI. For patients with advanced leukemia targeted TMI after TBI may be a novel approach to increase radiation dose with low risk of severe toxicity.