Comparison of Survival Outcomes of Breast-Conserving Surgery Plus Radiotherapy with Mastectomy in Early Breast Cancer Patients: Less Is More?

Purpose: To compare the survival outcomes of early-stage breast cancer patients treated with breast-conserving therapy (BCT) and mastectomy. Method: This retrospective study includes 1330 early-stage breast cancer patients treated at Chiang Mai University (CMU) hospital, using data from the Chiang Mai Cancer Registry between 2004 and 2015. Information pertinent to patients and their treatment was collected for analysis. Time-to-event analysis was performed using Kaplan-Meier methods. Results: The baseline characteristics of 1330 patients showed significant differences between the BCT and mastectomy groups in terms of age, tumor size, and tumor location. BCT patients were younger, had smaller tumors, and exhibited less nodal involvement. Propensity score matching created a balanced cohort of 534 patients where differences persisted in age and tumor size. Univariate analysis revealed significant survival associations for BCT, younger age, and smaller tumor size. Multivariate analysis confirmed these factors, with BCT showing an adjusted hazard ratio (HR) of 0.58 (95% CI: 0.36-0.93; p = 0.023) compared to mastectomy. Kaplan-Meier survival analysis demonstrated a significant survival advantage for BCT, particularly in HER2-enriched and triple-negative subtypes. The 15-year overall survival was 80.01% in the BCT group versus 64.33% in the mastectomy group (p < 0.001). Conclusions: This study reveals key differences between outcomes following breast-conserving therapy (BCT) and mastectomy patients, including age and tumor characteristics. BCT showed improved overall survival, particularly in HER2-enriched and triple-negative breast cancers. However, our study's limitations may affect the results. These findings suggest that BCT may offer survival benefits for specific subtypes, highlighting the importance of personalized treatment approaches.