Abstract PS1-07-16: Cosmesis Outcomes After Preoperative Radiation Boost for Early Breast Cancer

Abstract Purpose: Breast cosmesis is an important outcome for women after breast conservation surgery (BCS). Conventionally, radiation therapy (RT) is given after BCS, and often includes a boost to the lumpectomy cavity. However, in a recent phase 2 prospective trial, patients were treated with a preoperative RT boost of 1332 cGy in 4 fractions, followed by BCS and postoperative adjuvant whole breast RT of 3663 cGy in 11 fractions, resulting in a smaller boost volume than would be given with standard post-operative treatment. We hypothesize that there may be an improvement in patient- and physician-reported cosmesis when the boost is given preoperatively Materials and Methods: Single institutional cross-sectional study evaluating patients enrolled in the preoperative boost trial who completed the assigned treatment and were available for post-treatment analysis. Standardized photographs of patients were taken after completion of adjuvant whole breast RT, and cosmesis was evaluated using standardized scoring systems. Physician-rated cosmesis assessment was performed by a radiation oncologist and a surgical oncologist specialized in breast cancer using the 4-point Harvard cosmesis scale. Patient-reported outcomes were captured by the Breast Cancer Treatment Outcome Scale (BCTOS) questionnaire at 6-month intervals. Results: Photographs of 27 patients (n=27) were taken and assessed. Median age was 68 years. 22% of the patients had ductal carcinoma in situ (DCIS) with median tumor size of 6.5 mm and 78% had invasive pathology and median tumor size of 9.5 mm. Median time from adjuvant RT completion to photographic assessment was 2.5 years. 14% of patients had bilateral oncoplastic reduction at the time of BCS. Perceived differences by patients between the affected breast and contralateral breast were minimal at 1 year (median [IQR] BCTOS score 22 [20-26], with lowest possible score of 17, highest score of 68, and higher scores indicating greater differences. Inter-rater agreement between radiation and surgical oncologists for cosmetic outcome was assessed using weighted Cohen’s kappa. The kappa value was 0.691 (95% CI: 0.42-0.96), indicating substantial agreement. Rating of cosmesis post-RT by radiation oncologist was: 59% excellent, 36% good, and 7% fair, and surgical oncologist assessment was: 63% excellent, 36% good, and 3% fair. None of the assessed patients had poor cosmetic outcomes. Conclusion: In this prospective phase 2 clinical trial, administering the radiation boost pre-operatively, analysis of physician and patient-reported outcomes demonstrated an overall positive experience and acceptable cosmesis for trial participants. This may facilitate in the decision-making process for patients who have early breast cancer suitable for breast-conserving surgery and are considering various treatment options with radiation therapy. Further randomized trials will be required to compare the long-term effectiveness of pre-operative compared to post-operative boost approach. Citation Format: S. Mamidanna, M. Patel, K. Patel, R. Noziere, N. Ohri, A. Grann, D. Toppmeyer, S. Kumar, B. Haffty. Cosmesis Outcomes After Preoperative Radiation Boost for Early Breast Cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-07-16.