Efficacy and Safety of Adjuvant Radiotherapy for Soft Tissue Sarcoma: A Two-Institution Retrospective Observational Study

The recommended post-operative radiotherapy dose of approximately 60 Gy may be reduced during treatment planning, and the optimal irradiation method and dose remain unclear. We aimed to clarify the usefulness and safety of post-operative radiotherapy for soft tissue sarcomas. Forty-five patients with soft-tissue sarcomas who underwent adjuvant radiotherapy at two institutions from June 2014 to August 2020 were included. Patients with a high risk of recurrence underwent post-operative irradiation, with doses of 60–70 Gy and 50 Gy used in patients with positive and negative resection margins, respectively. The median patient age was 72 (21–88) years. The most common histological types of sarcomas were myxofibrosarcoma (n = 12) and dedifferentiated liposarcoma (n = 11), followed by other sarcomas. Thirty patients were newly diagnosed, and 15 underwent surgery for localized recurrent disease. Thirty-two and 13 patients underwent wide and marginal resection, respectively. Surgical margins were negative in 12 patients and positive in 33 patients. Chemotherapy was administered before or after radiotherapy in 16 patients. The 2-year local control, progression-free survival, and overall survival rates after post-operative radiotherapy were 88%, 78%, and 93%, respectively. In patients with positive resection margins, doses of ≥ 60 Gy contributed to local control (p = 0.0002, log-rank test) and progression-free survival (p = 0.0033). Late grade 3 adverse events were observed in 7% of the patients. Post-operative radiotherapy for soft tissue sarcomas is safe and effective, with high doses (≥ 60 Gy) contributing to reduced recurrence among patients with positive resection margins.