Long-term oncological outcomes after nipple-sparing mastectomy and implant-based immediate breast reconstruction in a large population-based cohort

Abstract Introduction The aim was to critically evaluate long-term local recurrence (LR) rates and overall survival (OS) after nipple-sparing mastectomy (NSM) versus skin-sparing mastectomy (SSM) in women with breast cancer receiving implant-based immediate breast reconstruction (IBR). Method We conducted a cohort study using the population-based Stockholm Breast Reconstruction Database, including all women with breast cancer who underwent implant-based IBR in the Stockholm region between 2005 and 2015. Data were collected retrospectively by individual medical chart review and further completed with data from the prospectively maintained National Quality Register for Breast Cancer. Endpoints were time from implant-based IBR to LR and all-cause death (OS), analysed with Kaplan-Meier methods and Cox regression. Result Among 1594 implant-based IBRs in 1537 women, 1376 (86.3%) were SSM and 218 (13.7%) NSM. Median follow-up was 75 months (range 1-198) for SSM and 60 months for NSM (range 1-170), P<0.001). NSM use increased over time (2005–2007: 25 (7.6%) to 2014–2015: 97 (26.6%), P<0.001). At 12 years since IBR, the cumulative incidence of LR was 6.4% (14 events) following NSM and 2.8% (28 events) following SSM (P<0.001), with an adjusted hazard ratio (HR) of 2.24 (95% confidence interval (CI) 1.11-4.51). OS did not differ significantly between NSM and SSM (HR 0.91, 95% CI 0.51-1.60). Discussion While the absolute risk of LR was low in both groups, NSM was associated with a higher relative risk than SSM, without compromising OS. This observed difference may be related to more residual breast glandular tissue following NSM; however, imaging studies are warranted to evaluate this hypothesis.