Oncologic Outcomes of Breast-Conserving Surgery in a Colombian Cancer Center: An Observational, Analytical, Retrospective Cohort Study

<b>Background:</b> Breast-conserving surgery (BCS) is one of the major surgical advances in breast cancer treatment. This study evaluated the oncological outcomes of BCS in patients with non-metastatic breast cancer at a referral cancer center in a medium-resource country between 2013 and 2019. <b>Methods:</b> An observational, analytical, retrospective cohort study was conducted on patients with stage I-IIIC breast cancer treated at the Instituto Nacional de Cancerología (Bogotá, Colombia) from September 2013 to March 2019. Demographic data, tumor characteristics, treatment types, and survival outcomes were retrospectively collected. <b>Results:</b> A total of 409 patients were included. In 64.1% of cases, BCS was performed as the initial treatment and in 35.9%, after neoadjuvant chemotherapy (NACT). With a median follow-up of 85.2 months, tumor recurrence was documented in 9.04% of patients, local recurrence in 2.9%, regional in 2.2%, and distant in 5.6%. The identified risk factors for mortality were a locally advanced clinical stage (HR 5.13; <i>p</i> = 0.01), triple-negative subtype (HR 8.02; <i>p</i> < 0.01), and nodal involvement of more than four lymph nodes in the surgical specimen (HR 4.00; <i>p</i> < 0.01). <b>Conclusions:</b> Breast-conserving surgery is an oncologically safe procedure for patients with early and locally advanced breast cancer who respond to NACT. The time to recurrence and overall survival are determined by the clinical stage, axillary tumor burden, and biological subtype of the disease.