Proton irradiation in sarcomaA prospective study of proton reirradiation for recurrent and secondary soft tissue sarcoma

Background and purposeProton reirradiation for sarcoma has not been previously described. We hypothesized that this strategy would provide favorable toxicity and survival outcomes.Material and methodsPatients with soft tissue sarcoma in a previously-irradiated field were enrolled on a prospective trial of proton reirradiation. The primary endpoint was provider-reported acute toxicity. Secondary endpoints included late toxicities, local control, and overall survival.Results23 patients underwent proton reirradiation. Median time between radiation courses was 40.7 months (range 10-272). No grade 4-5 toxicities were observed. One patient (4%) experienced acute grade 3 dysphagia. Common grade 2 acute toxicities were fatigue (26%), anorexia (17%), and urinary incontinence (13%). There were two grade 3 late wound infections (10%) and one grade 3 late wound complication (5%). Grade 2 late complications included lymphedema (10%), fracture (5%), and fibrosis (5%). At a median follow-up of 36 months, the 3-year cumulative incidence of local failure was 41% (95% CI [20-63%]). Median overall survival and progression-free survival were 44 and 29 months, respectively. In extremity patients, amputation was spared in 7/10 (70%).ConclusionsProton reirradiation of recurrent/secondary soft tissue sarcomas is well tolerated. While longer follow-up is needed, early survival outcomes in this high-risk population are encouraging.