# Risk of Breast and Ovarian Cancer After Prophylactic Mastectomy and Salpingo‐Oophorectomy in BRCA1/2 Germline Variant Carriers: A Retrospective Cohort Study From a Single German Center

## TL;DR

This study examines the effectiveness of prophylactic surgeries in reducing breast and ovarian cancer risks for women with BRCA1/2 gene mutations.

## Contribution

The study provides new insights into the effectiveness of mastectomy versus breast-conserving surgery in preventing ipsilateral secondary cancers in BRCA1/2 carriers.

## Key findings

- No breast cancer cases were observed after prophylactic bilateral mastectomy.
- Mastectomy showed lower rates of ipsilateral secondary cancer compared to breast-conserving surgery.
- Only 2.0% of patients who underwent PBSO had incidental ovarian cancer findings.

## Abstract

As the data on BRCA1/2‐associated breast and ovarian cancer prevalence after prophylactic surgery has not been exhaustively investigated yet, we aimed to evaluate the cancer prevalence in a single center cohort of BRCA1 and BRCA2 carriers after conducting prophylactic mastectomy, as well as prophylactic bilateral salpingo‐oophorectomy (PBSO) respectively.

We included 875 women that were tested positive for a germline variant in the BRCA1/BRCA2 gene (gPV) between 2002 and 2022 at the Center of Hereditary Breast and Ovarian Cancer of the Technical University Munich Germany. Mean follow up was 7.2 years (range 0–44 years; 95% CI: 6.70 to 7.70). We differentiated breast and/or ovarian cancer diseased (n = 643) and non‐diseased BRCA1/2 carriers (n = 232).

Our analysis confirmed the effectiveness of prophylactic surgeries in genetically predisposed women with a gPV in the BRCA1/2 gene. We observed no breast cancer after prophylactic bilateral mastectomy, 2 contralateral breast cancer diseases after contralateral prophylactic mastectomy and 1 extraovarian serous adenocarcinoma after PBSO. Within the entire study collective, a total of 293 have undergone PBSO, with 6 women having an incidental finding of ovarian cancer and STIC respectively (=2.0%; 1.7% gBRCA1 and 0.3% gBRCA2). Our data suggests that, particularly regarding ipsilateral secondary cancer (ISC), higher oncological safety can be achieved through mastectomy rather than breast‐conserving surgery (BCS). In the group of patients who had a second breast cancer and were treated with BCS during their first cancer, 18.3% showed an ISC. Within the patients who were first treated with a mastectomy, only 4.3% showed an ISC.

Prophylactic surgeries demonstrate high oncological effectiveness in gPV BRCA1/2 carriers. In particular, mastectomy may provide greater protection against ISC compared with BCS. Further studies will have to be conducted to compare ipsilateral cancer prevalence after breast‐sparing surgery and mastectomy.