Low Cancer Occurrence Rate following Prophylactic Nipple-Sparing Mastectomy.

Background: Nipple-sparing mastectomy (NSM) has become widely available for breast cancer prophylaxis. There are limited data on its long-term oncologic safety. The objective of this study was to determine the incidence of breast cancer in patients who underwent prophylactic NSM.

Methods: All patients undergoing prophylactic NSM at a single institution from 2006 through 2019 were retrospectively reviewed. Patient demographic factors, genetic predispositions, mastectomy specimen pathology, and oncologic occurrences at follow-up were recorded. Descriptive statistics were performed where necessary to classify demographic factors and oncologic characteristics.

Results: A total of 871 prophylactic NSMs were performed on 641 patients, with median follow-up of 82.0 months (standard error 1.24). A total of 94.4% of patients ( n = 605) underwent bilateral NSMs, although only the prophylactic mastectomy was considered. The majority of mastectomy specimens (69.6%) had no identifiable pathology. A total of 38 specimens (4.4%) had cancer identified in mastectomy specimens, with ductal carcinoma in situ being the most common (92.1%; n = 35). Multifocal or multicentric disease was observed in seven cases (18.4%) and lymphovascular invasion was identified in two (5.3%). One patient (0.16%), who was a BRCA2 variant carrier, was found to have breast cancer 6.5 years after prophylactic mastectomy.

Conclusions: Overall primary oncologic occurrence rates are very low in high-risk patients undergoing prophylactic NSM. In addition to reducing the risk of oncologic occurrence, prophylactic surgery itself may be therapeutic in a small proportion of patients. Continued surveillance for these patients remains important to assess at longer follow-up intervals.

Clinical Question/level Of Evidence: Risk, IV.