Abstract PO4-08-04: Comparison of Outcomes and Prognosis between BRCA Pathogenic Variant Carriers Undergoing Breast-Conserving Surgery versus Mastectomy for Breast Cancer

Abstract Introduction: While outcomes are similar following breast-conserving surgery (BCS) or mastectomy among patients with sporadic breast cancer, data are still controversial for germline BRCA pathogenic variant carriers. We previously compared outcome following BCS between BRCA pathogenic variant carriers and non-carriers, and reported higher ipsilateral breast recurrence and comparable prognosis in the carriers. The purpose of this current study was to compare outcomes among BRCA pathogenic variant carriers undergoing BCS versus mastectomy in long-term follow-up period. Methods: Women with a BRCA pathogenic variant and a stage 0-III breast cancer who underwent definitive surgery from 1987–2021 were retrospectively identified from institutional database. Factors including clinicopathologic information and treatment characteristics were identified. Subsequent local recurrence, regional recurrence, distant recurrence, contralateral breast cancer (CBC), breast cancer-specific survival (BCSS), and overall survival (OS) rates were compared between BCS and mastectomy using Kaplan-Meier method and log-rank test. The chi-square test and t-test were used to compare patient characteristics between the two groups. Results: A total of 232 BRCA mutation carriers with 257 cancers including 25 patients with synchronous bilateral breast cancer were identified. Surgical treatment included BCS for 82 cancers and mastectomy for 175 cancers including nipple-sparing mastectomy for 51 cancers. Patient age at surgery and cancer stage did not statistically differ between BCS and mastectomy groups. Comparing to patients choosing mastectomy, patients who underwent BCS were less likely to be aware of their genetic status before surgery and were more likely to receive radiation therapy (p 0.001). Contralateral risk reducing mastectomy was performed in 22.5% (18/80) in the BCS group and 48.7% (74/152) in the mastectomy group (p 0.001) concurrently or at any time after the first definitive surgery. Risk reducing salpingo-oophorectomy was performed in 40% (32/80) in the BCS group and 49% (75/152) in the mastectomy group (p = 0.17). At 7.5 years median follow-up, local recurrence rate was statistically higher in the BCS group than in the mastectomy group (20.0% in BSC vs. 4.6% in mastectomy, p = 0.043). In patients who underwent nipple-sparing mastectomy, 4.0% (2/51) had local subcutaneous recurrence and no nipple-areolar recurrence was observed. Median duration from the first definitive surgery to ipsilateral local recurrence was 10.0 years in the BCS group and 2.3 years in the mastectomy group. Regional lymph node recurrence (11.2% in BCS vs. 6.4% in mastectomy, p = 0.62), distant recurrence (13.7% vs. 9.2%, p = 0.84), CBC (15.0% vs. 8.6%, p = 0.70), BCSS (88.8% vs. 94.1%, p = 0.65) and OS (87.5% vs. 94.1%, p = 0.49) rates did not statistically differ between two groups. Conclusions: With 7.5 years median follow-up, higher local recurrence rate was observed in BCS than in mastectomy among BRCA pathogenic variant carriers. Our results found no statistical difference between BCS and mastectomy in regional recurrence, distant recurrence, CBC, and prognosis, indicating relatively higher risk in BCS. While BCS could be an option for BRCA pathogenic variant carriers willing to continue high-risk breast surveillance, shared decision making should be carefully performed based on the long-term local recurrence risk. Citation Format: Kumiko Kida, Junko Takei, Misato Suzuki, Megumi Okawa, Sakurako Kazama, Sakiko Kondo, Michiko Yamanaka, Atsushi Yoshida. Comparison of Outcomes and Prognosis between BRCA Pathogenic Variant Carriers Undergoing Breast-Conserving Surgery versus Mastectomy for Breast Cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-08-04.