There were 58,459 new cases of breast cancer in France in 2018 [1]. Only 5 to 10% of breast cancers are hereditary, i.e. attributable to a genetic mutation, whether known or not. Next Generation Sequencing (NGS) makes it possible to identify a panel of genes predisposing to breast cancer. BRCA2 mutation, followed by BRCA1 mutation are the two most frequent mutations [2]. Patients with BRCA1 and BRCA2 mutations have a higher risk of developing breast and ovarian cancer compared to the wild-type population. By age 80, the cumulative risk of developing invasive cancer is estimated to be 72% for patients with a BRCA1 mutation and 69% for patients with a BRCA2 mutation [3]. At twenty years after a first invasive cancer, the cumulative risk of developing a contralateral cancer is 40% for BRCA1 mutated patients and 26% for BRCA2 mutated patients [3]. Data from the literature confirm that the presence of a BRCA mutation significantly increases the rate of ipsilateral breast cancer [4,5] but also the rate of contralateral breast cancer [6].

The therapeutic management of early-stage breast cancer is based on four main approaches: surgery, radiotherapy, chemotherapy and hormonal therapy [7]. For localized cancers, breast-conserving surgery and sentinel lymph node biopsy are performed if the breast volume is amenable, combined with adjuvant radiotherapy and adjuvant systemic treatments if necessary. Total mastectomy is performed in cases of contraindication to radiotherapy, in cases of large tumors or in cases where the breast volume is insufficient to perform conservative treatment with a satisfactory aesthetic result, or at the patient's request. In the literature, there is no significant difference in terms of recurrence-free survival (RFS) or overall survival (OS) between conservative surgery with adjuvant radiotherapy versus total mastectomy in the population with early breast cancer and without known mutation [8], [9], [10].

For patients with a BRCA mutation, there are no specific recommendations for surgical management. There is currently no prospective randomized study that has compared conservative surgery versus mastectomy and conducting such a study would not be ethical. Retrospective studies on this subject are discordant. In the study by Pierce et al., the 15-year recurrence rate was significantly higher in the group undergoing conservative surgery and adjuvant radiotherapy, compared to patients undergoing total mastectomy for the surgical management of early breast cancer in patients with a BRCA mutation (23.5% vs. 5.5%, p<0.0001) [11]. In the study by Wan et al. comparing breast cancer severity score (BCSS) survival between conservative surgery, total mastectomy alone and mastectomy followed by radiation, for BRCA mutated patients, there was no significant difference between the three treatment strategies [12].

In this context, the aim of this study was therefore to retrospectively investigate overall survival (OS) and recurrence-free survival (RFS) of BRCA mutation positive patients with localized invasive breast cancer, by comparing conservative surgery versus mastectomy, using data from the Côte d'Or Registry of Breast and other Gynecological Cancers.