The effectiveness of radiotherapy in preventing disease recurrence after breast cancer surgery

Background and objectivesThe locoregional management of breast cancer has a critical impact on prognosis. This study aimed to analyze the effectiveness of radiotherapy against the deleterious effect of positive surgical margins on disease outcomes.MethodsRetrospective, single-center study enrolled 721 breast cancer patients with a median follow-up of approximately 64.50 months (3.67–247.40). Analyses were performed considering the end of adjuvant therapy, except endocrine therapy. Kaplan-Meier and Cox regression were performed to obtain the predictive value of treatments.ResultsThe minimally adequate radiotherapy (≥45 cGy) was associated with improved outcomes in breast cancer patients compared to inadequate radiotherapy (<45 cGy/no) by controlling locoregional relapses and distant metastasis. In patients with positive surgical margins (n = 53), radiotherapy was associated with an approximate decrease of 90% in locoregional relapse risk adjusted HR: 0.108 (0.012–0.932), p = 0.043]. Radiotherapy did not alter the adverse effect of positive surgical margins, especially in patients with a higher risk of poorly differentiated tumors (n = 146), presence of lymphovascular invasion (n = 163), and triple-negative subtype (n = 113). Notwithstanding, radiotherapy was associated with respective decreases of distant metastasis risk of 75.2% adjusted HR: 0.248 (0.081–0.762), p = 0.015] and 67.8% adjusted HR: 0.322 (0.101–1.029), p = 0.056] in patients with triple-negative tumors or with lymphovascular invasion.ConclusionAdequate radiotherapy is associated with better outcomes in breast cancer. Despite improving locoregional relapse-free survival, radiotherapy does not ablate positive surgical margins, a factor of poorer prognosis that prevails mainly in patients with factors of higher relapse risk.