Abstract PS2-05-11: Early oncologic outcomes of robot-assisted versus conventional nipple-sparing mastectomy: a propensity score matching analysis

Abstract Background: Robot-assisted nipple-sparing mastectomy (R-NSM) was developed to minimize visible scarring and improve the quality of life in breast cancer patients. However, despite its increasing adoption, data on its oncologic outcomes remain limited. This study aimed to compare the oncologic outcomes of R-NSM and conventional nipple-sparing mastectomy (C-NSM). Methods: We retrospectively reviewed patients who underwent NSM with immediate breast reconstruction (IBR) for breast cancer between 2019 and 2022. Risk-reducing cases were excluded. R-NSM and C-NSM groups were compared after 1:5 propensity score matching using nearest-neighbor methods (caliper = 0.2). Results: After 1:5 propensity score matching, most clinicopathologic variables were well balanced between groups. The median follow-up duration was 37.5 months for the R-NSM group and 42.6 months for the C-NSM group. No locoregional recurrence, distant metastasis, or death occurred in the R-NSM group. All oncologic events occurred in the C-NSM group, including 3 locoregional recurrences (1.5%), 3 distant metastases (1.5%), and 7 total recurrences (3.5%). Kaplan-Meier analysis showed no statistically significant differences in LRFS (p = 0.162), DMFS (p = 0.255), or DFS (p = 0.050), though all adverse events occurred in the C-NSM group. Event-based comparison revealed a significantly better DFS for R-NSM (p = 0.002). In multivariable Cox analysis, older age (HR = 0.14, p = 0.040) and positive nodal stage (N1: HR = 4.7; N3: HR = 31.9, p = 0.042) were associated with increased recurrence risk. R-NSM showed a lower recurrence hazard in univariable analysis (HR = 0.12, p = 0.177). Conclusion: R-NSM showed oncologic outcomes comparable to those of conventional NSM, with no recurrence or mortality observed despite longer follow-up. These results support R-NSM as a safe and effective surgical option for appropriately selected breast cancer patients. Citation Format: S. Lee. Early oncologic outcomes of robot-assisted versus conventional nipple-sparing mastectomy: a propensity score matching analysis [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-05-11.