ESTRO 2024 - Abstract Book

S197

Brachytherapy - GI, paediatric, miscellaneous

ESTRO 2024

2966

Proffered Paper

Recurrence patterns after multimodal treatment including IORT for extremity soft tissue sarcomas

Elena Riggenbach 1 , Adam Zabini 1 , Attila Kollàr 2 , Frank Michael Klenke 3 , Christophe Kurze 3 , Radu Olariu 4 , Ioana Lese 4 , Emanuel Stutz 1 , Kristina Lössl 1 , Codruta Ionescu 1 1 Inselspital, Bern University Hospital and University of Bern, Department of Radiation Oncology, Bern, Switzerland. 2 Inselspital, Bern University Hospital and University of Bern, Department of Medical Oncology, Bern, Switzerland. 3 Inselspital, Bern University Hospital and University of Bern, Department of Orthopaedic Surgery and Traumatology, Bern, Switzerland. 4 Inselspital, Bern University Hospital and University of Bern, Department of Plastic and Hand Surgery, Bern, Switzerland

Purpose/Objective:

Multimodal therapy combining conservative surgery with radiotherapy allows for organ and function preservation in soft tissue sarcomas of the extremity (eSTS). Intraoperative radiotherapy (IORT) as a boost allows precise delivery of a single tumoricidal dose to areas of potential residual microscopic disease while effectively sparing radiosensitive structures. We assessed patterns of relapse in eSTS patients receiving high-dose-rate (HDR)-IORT.

Material/Methods:

Patients with primary eSTS that received an intraoperative boost with HDR-brachytherapy as part of their multimodality treatment between 2013 and 2019 were retrospectively reviewed. IORT was applied using a flab applicator (flexible silicone-based surface mold) with a dose of 10 Gy prescribed to 0.5cm depth. During systematic follow-up toxicities and recurrence profiles were assessed. Survival analysis was carried out with Kaplan-Meier method.

Results:

52 consecutive patients received IORT-boost to the tumor bed of the extremity. EBRT with 50 Gy in 2Gy / fraction was given as a neoadjuvant treatment in 31 patients (59.6%) and as adjuvant treatment in 20 patients (38.5%). One patient did not receive EBRT. 8 patients (15.4%) received chemotherapy. At a median follow-up of 67 months (range, 28-118) 20 patients (38.4%) developed a relapse: Isolated local recurrence occurred in 2 patients (3.8%) while synchronous local and distant recurrence occurred in 3 patients (5.8%). 15 patients (28.8%) developed isolated metastatic recurrence. The median time to event was 21 months for local recurrences and 12 months for distant recurrences. Of all distant relapses, 50% occurred in the first year, with a further 28% occurring in the second year. Severe late grade 3 toxicities were recorded in 5 patients (9.6%). No late grade ≥ 4 toxicity occurred. Extremity preservation in long-term follow-up was 100%. Local and distant control rates were 90.0%/67.3% at 5 years. Progression-free survival (PFS) and overall survival (OS) were 55.8%/61.9% at 5 years.

Conclusion: