(P 200) CLINICAL CHARACTERISTICS, PATTERNS OF CARE, AND TREATMENT OUTCOMES OF RADIATION-ASSOCIATED SARCOMAS

Objective: Radiation- associated sarcoma (RAS) are an extremely rare form of sarcoma, occurring in less than 1% of all exposed patients, children and adults alike. Prognosis for these aggressive tumors is poor, making RAS an arduous challenge for a significant minority of cancer survivors. With limited data to guide prevention and management, there exists a need for retrospective analysis at institutions that treat RAS. In this study, we aim to describe clinical presentation, patterns of care, and outcomes for RAS patients seen at our institution.

Methods: We performed a retrospective record review on all sarcoma patients seen at our institution from January 1, 2015 to January 20, 2021. Through a combination of data mining and manual chart verification, we identified RAS patients as those with a history of radiation therapy to the site of subsequent sarcoma diagnosis. No specific latency threshold was required.

Results: Twenty-one patients RAS patients were identified. Median age at diagnosis of RAS was 53.5 and median interval from primary RT was 11.6 years. RAS was most commonly located in the head and neck (47.6%), abdomen/pelvis (38.1%), and thorax (14.3%). Most common RAS histologies were undifferentiated pleomorphic sarcoma (23.8%) and leiomyosarcoma (19%). Median size was 4.8 cm, and 71.4% were high-grade. 23.8% had metastatic disease at presentation. Recurrent molecular features included TP53 loss-of-function mutations (42.8%), Rb1 deletion or loss-of-function mutations (14.3%),and loss-of-function mutations in CDKN2A and NF2 (9.5% each). 33% received RT and 38% underwent surgery. Among the entire cohort, median progression-free survival was 7.8 mo and median overall survival was 9.6 mo.

Conclusion: RAS can develop with variable latency following radiation therapy. Outcomes in this disease remain challenging, though some patients can experience prolonged survival. Further study is necessary to characterize the prognostic factors and optimal treatment approaches for these patients.