Oncologic safety of prophylactic nipple-sparing mastectomy: Outcomes of 1,255 cases exceeding a 6-year median follow-up.

[BACKGROUND] Prophylactic nipple-sparing mastectomy (PNSM) is performed to prevent the development of breast cancer. Despite the increasing usage of PNSM, large-cohort, long-term follow-up data is lacking. We aim to review a large cohort of PNSM cases to evaluate oncologic outcomes.

[METHODS] We retrospectively reviewed all PNSMs between 2000 and 2021 at a single institution. Clinicopathologic variables were collected and analyzed. Descriptive statistics and Kaplan Meier (KM) based survival analyses were used.

[RESULTS] A total of 1,255 PNSMs in 972 patients were performed from 2000 to 2021 with a median age of 43 years (IQR 37, 49) and a median follow-up of 81.3 months (IQR 50.8, 123.0). There were 38 (3.0%) cases of incidental breast cancer discovered on surgical pathology. There were 3 (0.3%) new primary breast cancer occurrences after PNSM. The KM estimates for 5-year rates in the entire cohort (n = 972) of incidence of new breast cancer, breast cancer-related mortality, and overall mortality were as follows: 0.15% (95%CI 0, 0.44%), 0.93% (95%CI 0.28%, 1.57%), and 1.63% (95%CI 0.78%, 2.48%), respectively. The KM estimates for 5-year rates in the BRCA-only cohort (n = 333) of incidence of new breast cancer, breast cancer-related mortality, and overall mortality were as follows: 0.44% (95%CI 0, 1.30%), 1.75% (95%CI 0.21%, 3.26%), and 2.09% (95%CI 0.42%, 3.73%), respectively.

[CONCLUSION] New primary breast cancer infrequently developed after PNSM in this study. Incidental breast cancer was identified on surgical pathology in a small subset of patients. PNSM may be associated with preventing breast cancer development.