Secondary sarcomas after radiotherapy for breast cancer

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Abstract
BACKGROUND: Radiotherapy (RT) has been a risk factor for development of soft tissue sarcomas (STS). The objective of the current study was to quantify the risk of STS after RT and surgery for breast cancer (BCa), assess time trends, and compare long‐term survival of patients with RT‐associated and non–RT‐associated angiosarcoma (AS) using the Surveillance, Epidemiology, and End Results (SEER) database. METHODS: Women with BCa reported to SEER in 1973 to 2003 were included. Kaplan‐Meier curves and proportional hazards models, reported as hazards ratios (HR) with 95% confidence intervals (95% CI), were used. Survival of patients who developed RT‐associated AS was compared with that of patients with primary AS of the thorax and upper extremities. RESULTS: The cohort of 563,155 BCa patients was divided into 2 groups: those who received RT (37%) and those who received no RT. RT use increased with time (P <. 0001). A total of 948 patients developed STS 1 to 29 years after BCa diagnosis. RT patients had a higher incidence of all STS (31 vs 22 per 100,000 person‐years; HR, 1.5 [95%CI, 1.3‐1.8]), AS (HR, 7.6; 95% CI, 4.9‐11.9), and malignant fibrous histiocytomas (MFH) (HR, 2.5; 95% CI, 1.6‐3.9). RT remained a significant predictor after adjustment for covariates (HR, 1.4; 95% CI, 1.2‐1.7). Partial mastectomies (HR, 7.1; 95% CI, 3.2‐16), RT (HR, 2.2; 95% CI, 1.1‐4.3), and lymph node dissections (HR, 2.6; 95% CI, 1.3‐5) were found to be independent risk factors for AS. The hazard of STS after RT peaked at 10 years, reaching the non‐RT hazard at approximately 23 years. The 5‐year survival for STS was 38%. There was no difference in survival noted between RT‐induced and non–RT‐induced AS. CONCLUSIONS: RT was found to increase the risk for STS, in particular AS and MFH. Patients who received RT for BCa should be followed closely for >20 years. Cancer 2009. © 2009 American Cancer Society.