Preoperative stereotactic ablative body radiotherapy with postoperative conventional irradiation of soft tissue sarcomas: Protocol overview with a preliminary safety report.

Unlabelled: Preoperative radiotherapy in patients with soft tissue sarcomas is characterized by important advantages: high precision of dose delivery, reduction of tumor volume and implantation potential, induction of immunologic response. Postoperative irradiation is associated with a reduced risk of complication, and a comprehensive radiotherapy planning in accordance with the pathologic report. Combination of pre- and postoperative irradiation gives the opportunity to use the best of both methods.

Objective: To analyze feasibility and safety of radiotherapy protocol that combined pre- and postoperative radiotherapy in patients with soft tissues sarcomas of extremities.

Materials And Methods: From 06.2018 to 01.2021, 23 patients with soft tissue sarcomas of extremities were included in the protocol (NCT04330456) and 14 cases with at least 12 months follow-up were eligible for analysis. Preoperative stereotactic ablative body radiotherapy (SBRT) was performed as 5 fraction of 7 Gy with dose reduction (5 fractions of 5 Gy) on the margins of the tumor. Postoperative radiotherapy started 5-8 weeks after the surgery and was performed as standard compartmental irradiation in 25 fractions of 2 Gy. Complications were determined according to CTCAE and wound complication scales.

Results: Preoperative SBRT and subsequent radical resection with tumor free surgical margins were performed in all 14 cases. Primary wound closure was mentioned in all patients. Postoperative radiotherapy started 51.8 days (range 33-99 days) days after the surgery. With a relatively short follow-up of 21.5 (13-30) months, we recorded 2 cases (14%) of severe complications (Canadian sarcoma group criteria), and there were no local recurrences.

Conclusion: Our preliminary results demonstrate that the combination of preoperative SBRT and postoperative conventional radiotherapy is feasible and does not increase the risk of postoperative complications.