High-dose carbon ion re-irradiation for recurrent pelvic sarcomas: a retrospective analysis of oncologic outcomes in a referral center.

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Purpose To evaluate the safety and efficacy of high-dose carbon ion re-irradiation (CIR) in patients with recurrent pelvic sarcomas. Material and methods This retrospective study included 46 patients treated with high-dose CIR for locoregional recurrences of pelvic sarcomas between 2013 and 2023 at the National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy. Clinical outcomes, toxicity and cumulative doses were analyzed. Results The median prescribed total dose of CIR was 60 GyRBE (range, 45-73.6). The maximum cumulative EQD2 to the target volume reached 284 Gy, with a median of 153 Gy. The median follow-up was 32.5 months. The 1-, 2-, and 3-year locoregional progression-free survival (LRPFS) rates were 79.1%, 43.9%, and 25.1%, respectively, with a mean time to locoregional relapse of 18.9 months. The 1-, 2- and 3-year overall survival (OS) rates were 100%, 93.9% and 83.1%, respectively. At last follow-up, grade 3 neuropathy occurred in 6.5% of the patients, grade 3 anorectal dysfunction in 8.7%, and grade 3 skin toxicity in 6.5%. Conclusions High-dose CIR is a feasible salvage strategy for recurrent pelvic sarcoma, offering promising outcomes and manageable toxicity in carefully selected patients. Prospective studies are warranted to refine dose-response models and validate long-term efficacy.