Highly cosmetic and safe breast-conserving surgery using a wave-like periareolar incision with sub-nipple and extensive subcutaneous dissection: a retrospective cohort study.

BACKGROUND: In breast-conserving surgery (BCS), tumor-surface incision often results in visible scarring, skin contracture, and nipple deviation. While various oncoplastic-BCSs (OBCSs) have been developed, many remain invasive and non-standardized. We developed a novel OBCS, namely, the Keio-BCS (K-BCS), utilizing a linear or wave-like periareolar incision combined with sub-nipple and extensive subcutaneous dissection, aiming for superior cosmetic outcomes across diverse patient and tumor characteristics. We aimed to compare cosmetic and surgical outcomes between K-BCS and tumor-surface incision surgery. METHODS: We retrospectively analyzed 195 patients who underwent BCS between January 1, 2021 and December 31, 2023 (K-BCS group, n=127; tumor-surface incision group, n=68). Cosmetic outcomes, objectively evaluated using BCCT.core software, were categorized as excellent, good, fair, or poor. Subgroup and logistic regression analyses were conducted for evaluation of 'excellent' outcome. Complication rates and the frequency of positive or close surgical margins (<2 mm) were also evaluated. RESULTS: The K-BCS group showed significantly better cosmetic outcomes than the tumor-surface incision group (excellent, 57% vs. 34%; good, 37% vs. 47%; fair, 5% vs. 16%; poor, 1% vs. 3%, respectively; P=0.002). Superior results with K-BCS were consistent across all subgroups. Multivariate analysis confirmed K-BCS as an independent factor associated with 'excellent' evaluation [odds ratio (OR) =2.58; 95% confidence interval (CI): 1.26-5.32; P=0.009]. No significant differences were observed in complication rates or margin status. CONCLUSIONS: As a promising, reproducible OBCS approach, K-BCS yielded superior esthetic outcomes across various patients and tumor characteristics while maintaining oncologic and surgical safety.