(P 262) EVALUATING FRONT-LINE THERAPY ACCORDANCE WITH CURRENT SYNOVIAL SARCOMA GUIDELINES

Objective: The standard treatment of synovial sarcoma (SS) consists of surgery with or without chemoradiotherapy and is stratified by tumor features and extent of surgery. Current pediatric practices are based on ARST0332 which utilized chemoradiotherapy for high grade localized disease >5 cm, while NCCN guidelines suggest only consideration of chemoradiotherapy for tumors >5 cm (T2 and higher) in adults. Given this variation, it is important to understand how this has been translated into practice. In this study, we assessed front-line therapy in the national SS Registry & Biospecimen Repository (SSRBR).

Methods: The SSRBR was established at the Children’s Hospital of Philadelphia. Informed consent was completed and medical records were obtained from treating institutions with updates every 6 months. Treatment was evaluated across pediatric ( < 18 years) and adult (≥18 years) populations. This analysis includes patients enrolled in the SSRBR in the first 14 months (cut-off July 31, 2024).

Results: Fifty-two patients were enrolled and 2 were excluded due to incorrect initial diagnosis. Of the 50 evaluable patients, 43 (86%) had localized disease and 7 (14%) had metastatic disease. Of the 43 patients with localized disease, all underwent surgical resection, 32 (71%) received chemotherapy, and 21 (47%) had radiotherapy. All patients with metastatic disease received chemotherapy, four (57%) underwent surgical resection and two (29%) received radiotherapy. Notably, there was a difference in chemoradiotherapy utilization for patients with tumors >5 cm across the pediatric and adult populations (Table 1).

Conclusion: Within the SSRBR, patients received care consistent with treatment guidelines. When stratified by age, there was an observed difference in the use of chemoradiotherapy for localized disease >5 cm, which may reflect the variation in pediatric and adult practice. Analysis of factors contributing to the difference in chemoradiotherapy use is ongoing.

Table 1. Front-Line Therapy Received in Patients with Localized Disease*