(P 276) RADIATION-INDUCED SARCOMA (RIS): CLINICAL SPECTRUM AND ONCOLOGIC OUTCOMES FROM A TERTIARY INDIAN SARCOMA CLINIC

Objective: Radiation-induced sarcoma (RIS) is a rare but highly aggressive late complication of therapeutic radiotherapy. Data on RIS in the Indian population are limited, and optimal treatment strategies remain undefined. This study aimed to evaluate the clinicopathological characteristics, treatment patterns, and outcomes of patients diagnosed with RIS at a tertiary sarcoma referral center.

Methods: A retrospective analysis was conducted of a prospectively maintained sarcoma database at the All India Institute of Medical Sciences (AIIMS), New Delhi. Patients diagnosed with biopsy-proven RIS between January 2015 and June 2025 were included. Clinical, pathological, and treatment data were extracted from institutional records. Survival outcomes, including overall survival (OS), were estimated using the Kaplan–Meier method. Group-wise comparisons (metastatic vs. non-metastatic) were performed using the log-rank test using SPSS V.30.

Results: A total of 23 patients (0.32% of 7,138 sarcoma cases evaluated) were diagnosed with radiation-induced sarcoma (RIS). The median age at RIS diagnosis was 51.1 years, and the median latency from radiotherapy was 13.25 years. Breast cancer (21.7%) was the most frequent primary malignancy. Soft tissue sarcomas were more common (60.9%), with undifferentiated pleomorphic sarcoma being the predominant histological subtype (34.8%). At diagnosis, 52.2% had metastatic disease, while 13.1% were locally unresectable. Most tumors were high-grade (87.0%) with a median size of 6.9 cm. Surgery was performed in 7 out of 8 patients with resectable disease, achieving R0 resection margins in 62.5% of cases. Re-irradiation was administered in 3 patients. A total of 16 patients (69.6%) received systemic therapy comprising heterogeneous regimens. The most commonly used regimen was single-agent doxorubicin (n = 5), followed by combination therapy including doxorubicin, ifosfamide, and platinum (n = 3), among others. For those who received systemic therapy, partial response was observed in 12.5% of patients, while stable disease was achieved in 31.3%. Median follow-up was 68.2 months. The overall median survival was 50.9 months, with a non-significant survival difference between metastatic and non-metastatic patients (13.4 vs. 59.2 months, log-rank p = 0.07).

Conclusion: In this largest single-institution series of RIS from India, the majority of patients presented with large tumor size, high-grade, and metastatic or unresectable disease. Despite these unfavorable characteristics, curative-intent surgery was achieved in most non-metastatic cases, and systemic therapies were employed across various clinical settings. The higher median OS is encouraging, particularly within the context of LMIC, highlighting the value of centralized, multidisciplinary sarcoma care even in resource-constrained environments.