2799 - Contralateral Breast Dose among Young Patients Receiving Breast Radiotherapy: Incidence and Implications
Presenter(s)
A. L. Matous1, E. Chen2, D. A. Alexander1, and L. A. Jarvis3; 1Dartmouth-Hitchcock Medical Center, Lebanon, NH, 2Cheshire Medical Center, Keene, NH, 3Dartmouth Health, Lebanon, NH
Purpose/Objective(s): The incidence of breast cancer in young patients is rising, expanding the population at risk for radiation-associated late effects. Because these patients often have decades of survivorship ahead, minimizing radiation exposure to uninvolved tissues is critical. Dose to the contralateral breast is a well-established risk factor for radiation-induced secondary malignancies, as demonstrated in the WECARE study, with younger age at exposure conferring substantially higher lifetime risk. However, the magnitude of contralateral breast dose (CBD) in modern radiotherapy practice remains incompletely characterized. Cherenkov imaging enables real-time visualization of treatment beam delivery on patient surfaces and may provide a practical method to detect unintended off-target dose, including CBD. We hypothesized that Cherenkov imaging could be used to provide accurate determination of CBD among a cohort of patients treated with modern radiotherapy techniques.
Materials/Methods: Cherenkov images for patients receiving breast radiotherapy at 1 academic and 1 community medical center were prospectively reviewed over 16 months as part of an ongoing clinical study. Patients treated in the supine position were evaluated for evidence of CBD, followed by root-cause analyses (RCA) to determine contributing factors. Demographics were noted, with a special focus on age given increasing numbers of young patient referrals
Results: Among the 310 unique patients and 4,542 images reviewed, there were 45 (15%) patients and 702 (15%) images from patients age 50 or younger. In this cohort of young patients, CBD was detected on images for 42% (19 / 45). The techniques associated with CBD in young patients were tangents (6), wide tangents (9), post-mastectomy volumetric modulated arc therapy (VMAT) (2), and accelerated partial breast radiotherapy with VMAT (2). RCA attributed CBD to unplanned causes such as setup issues in 68% (13 / 19) of cases.
Conclusion: Cherenkov imaging can be used to identify CBD among patients receiving breast radiotherapy, including young patients who are at greatest risk for radiation-associated malignancies. The detection of CBD in a substantial proportion of young patients underscores the need for further investigation in this high-risk group. Next steps include analyzing absolute, spatially resolved dose distributions to better quantify off-target exposure; comparing measured CBD with planned CBD; and leveraging RCA findings to implement risk-reduction strategies aimed at minimizing CBD in young patients.