Resident University of Wisconsin Madison School of Medicine and Public Health Madison, Wisconsin, United States
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Participants should be aware of the following financial/non-financial relationships:
Alyssa Wiener, MD: Disclosure information not submitted.
Introduction: Radiation-associated sarcoma (RAS) is a rare complication of radiation therapy for breast cancer. Since the first descriptions of RAS, radiation therapy modalities for breast cancer treatment have changed significantly. We sought to determine if the incidence of RAS after breast cancer treated with breast conservation and radiation (BCT) has changed over time.
Methods: The Surveillance, Epidemiology, and End Results (SEER) Program was used to identify breast cancer survivors (diagnosed 1988-2012) who were treated with BCT with the following exclusion criteria: patients who were male, ≤18 years, had history of prior cancer, had< 1y follow-up/survival, and who didn’t receive external beam radiation (final cohort n=276,301). We identified patients who subsequently developed a chest soft tissue sarcoma, excluding diagnoses within 1y of breast cancer diagnosis. Incidence of sarcoma after breast cancer by 5-year periods of breast cancer diagnosis year was estimated using Kaplan-Meier survival analysis. Patients were censored at the time of sarcoma diagnosis, death, last follow-up (available through 12/2017), or at 10-years post-breast cancer diagnosis. Given the known latency for RAS, we used Joinpoint analysis to identify the time point at which the rates of RAS incidence significantly increased. We used this point (5-years post-breast cancer diagnosis) as the start of the analytic window. A log-rank test was then used to assess differences in the survival functions of the diagnosis year groups.
Results: Overall incidence of RAS was 0.03% at 5-years (95% CI: 0.03-0.04%) and 0.16% at 10-years (95% CI: 0.14-0.18%) (Figure). There was no statistical difference in RAS incidence across the 5-year period diagnosis year groups (p=0.5).
Conclusions: Radiation-associated sarcoma consistently remains a rare but possible event for breast cancer survivors treated with breast conservation and external beam radiation. As new radiation modalities such as partial breast and hypofractionated regimens become more common, ongoing surveillance is necessary to track these rare events.
Learning Objectives:
describe the 5- and 10-year cumulative incidence of radiation-associated sarcoma in breast cancer survivors receiving breast conserving surgery and radiation
describe the impact of breast cancer diagnosis year on radiation associated sarcoma incidence
describe the time point after breast cancer diagnosis at which rate of radiation associated sarcoma increases
