Abstract P3-19-13: Radiation oncology treatment planning in breast cancer patients undergoing lumpectomy with and without oncoplastic reconstruction

Abstract

Abstract Background Breast conserving surgery (BCS) followed by whole breast irradiation with a tumor bed boost is a common approach for locoregional treatment of patients with breast cancer. While tumor bed boost improves local control, it is also associated with increased risk of fibrosis and fat necrosis. Oncoplastic reconstruction is being increasingly employed to improve cosmesis and symmetry with the contralateral breast following partial mastectomy. The extensive rearrangement of breast tissue during oncoplastic reconstruction has the potential to increase tumor bed volume, thereby increasing the volume of breast receiving a higher dose of radiation. In this study, we aimed to elucidate the current rise in use of oncoplastic reconstruction following breast-conserving surgery in patients with breast cancer and its impact on the volume of tumor bed as contoured by attending radiation oncologists at the time of radiation treatment planning. Methods A retrospective chart review of 331 women, who underwent breast conserving surgery at our institution between Jan 2020 and March 2021 for treatment of breast cancer was conducted. Patient demographics and tumor characteristics, including clinical and pathological staging, tumor receptor status, and tumor histology were recorded. Treatment-related information such as type of oncoplastic reconstruction where applicable, receipt of systemic therapy, dose and fractionation of radiation therapy, treatment technique and volume of tumor bed defined at the time of radiation treatment planning were collected. Results The median age of the cohort was 61, and 54.7% of patients received oncoplastic reconstruction. A plastic surgeon was involved in reconstruction in 22.8% of patients. Complex tissue advancement closure was the most common oncoplastic reconstruction employed in this cohort. A two-tailed T-test assuming unequal variances demonstrated that oncoplastic reconstruction was associated with a contoured tumor bed that was on average almost 10 mL larger (35.5 vs. 26.6 mL, p < 0.02). Conclusion Over half of patients receiving breast conserving surgery at our institution underwent oncoplastic reconstruction. The rate of oncoplastic reconstruction in this cohort was significantly higher than historic rates reported in the literature, likely reflecting an exponential growth in adoption of this approach in the United States. Use of oncoplastic reconstruction was associated with larger tumor bed volume at the time of radiation treatment. Although tumor bed boost improves local control, it also increases risk of fibrosis and fat necrosis. Therefore, further studies are needed to determine if larger volume of tumor bed irradiated in patients receiving oncoplastic reconstruction is associated with decline in long term cosmetic outcomes due to fibrosis and fat necrosis. Increased multi-disciplinary communication and collaboration between surgical oncologists, reconstructive surgeons and radiation oncologists is necessary to address the competing interests between breast reconstruction and irradiation following breast conserving surgery in patients undergoing breast conserving surgery for treatment of breast cancer. Citation Format: Brian Ko-Hung Lue, Ev Kakadiaris, Prasanna Alluri, M.D. Radiation oncology treatment planning in breast cancer patients undergoing lumpectomy with and without oncoplastic reconstruction [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-19-13.