Impact of Locoregional Treatment on Survival in Young Patients with Early-Stage Breast Cancer undergoing Upfront Surgery.

BACKGROUND: Randomized, controlled trials comparing breast-conserving therapy (BCT) with mastectomy have demonstrated equivalent overall survival (OS), but recent observational studies have shown improved OS in patients undergoing BCT. These studies provide limited data on young patients who are traditionally offered mastectomy due to perceived higher disease risk. This study examines the OS in a contemporary series of young women with breast cancer undergoing upfront BCT compared with mastectomy. METHODS: Women ≤40 years old with primary invasive T1-T2, N0-N1 breast cancer were identified from the National Cancer Database between 2006 and 2016. Patient cohorts were based according to locoregional treatment: BCT, mastectomy alone (Mx), and mastectomy with radiotherapy (Mx/RT). Kaplan-Meier method followed by Cox proportional-hazards regression with inverse probability of treatment weighting (IPTW) were performed to account for treatment selection bias effects in OS. RESULTS: A total of 15,611 patients met the study criteria; 9,509 patients (60.9%) had BCT, 4,020 (25.8%) had Mx/RT, and 2,082 (13.3%) had Mx alone. The median follow-up was 4.6 years (interquartile range [IQR] 3.0-6.4). After IPTW-adjustment, the 5-year OS was similar for BCT (95%), Mx (95%), and Mx/RT (94%), and there was no significant difference in OS in Mx (hazard ratio [HR] = 1.16, 95% confidence interval [CI] 0.90-1.51) and Mx/RT (HR = 1.08, 95% CI 0.88-1.34) compared with BCT. Mx/RT was associated with decreased survival in patients with pT2N0 (HR = 1.78, 95% CI 1.12-2.84). CONCLUSIONS: Among young patients with early-stage breast cancer, overall survival was equivalent regardless of surgical approach. Breast-conserving therapy remains a safe option in young women despite the clinical tendency to offer upfront mastectomy in young patients