Preliminary results of helical tomotherapy for total marrow irradiation

Objective To evaluate the efficacy and safety of total marrow irradiation (TMI) as the pretreatment before allogeneic peripheral blood stem cell transplantation (Allo-PBSCT). Methods From 2014 to 2015, six patients undergoing TMI combined with cyclophosphamide (60 mg/kg, once a day for 2 days) as the pretreatment before Allo-PBSCT were enrolled as subjects. The pretreatment was performed by helical tomotherapy (HT). Results The median age of the six patients was 18.5 years. The prescribed dose (12 Gy in 3 fractions for 3 days) accurately covered all bone regions. Compared with the total body irradiation, the dose to organs at risk was reduced by 13% to 60% in TMI. The passing rates for the doses to head-neck, chest-abdomen, and pelvic cavity were (95.8±1.2)%, (96.2±1.1)%, and (99.0±0.5)%, respectively. The homogeneity indices for the upper and lower parts were 1.18 and 1.17, respectively, while the average treatment durations for the upper and lower parts were 39.2 and 14.3 min, respectively. During radiotherapy, five patients had grade 1-2 nausea and vomiting, two grade 1-2 pain, one grade 1 diarrhea, and one grade 2 enteritis. There was no grade 3-4 non-hematological toxicity in patients. Bone marrow was successfully implanted in all patients. Conclusions HT is a feasible approach for TMI, with satisfactory dose homogeneity, high conformity to the target volume, high safety, and substantially reduced toxicities compared with total body irradiation. HT can be used as a novel method for the pretreatment before bone marrow transplantation. Key words: Total marrow irradiation; Total body irradiation; Tomotherapy; Bone marrow transplantation