Outcomes From Real-World Data on Intraoperative Electronic Radiotherapy for the Treatment of Early-Stage Breast Cancer: Long-Term Recurrence and Survival Outcomes From a Single Center

This study is aimed at investigating the 10-year outcomes of intraoperative radiotherapy (IORT) in Mexican women with early breast cancer (EBC) treated at the Centro Medico ABC, Mexico City. A cohort study included women with early-stage invasive ductal carcinoma aged ≥ 45 years without prior oncologic treatment, tumor size ≤ 3.5 cm, cN0M0, positive hormone receptors, margins ≥ 2 mm, negative sentinel lymph nodes, and no extensive lymphovascular invasion. IORT was administered at 20 Gy for 20-30 min after a lumpectomy. Follow-up extended over 10 years and included clinical examinations every 6 months for the first 18 months, followed by annual mammograms and conventional examinations. Patients out of the criteria were excluded from this study because they were referred for additional surgery and/or whole-breast radiation therapy. The study involved 238 patients with an average age of 61.1 years. The mean tumor size was 12 mm, and the percentages of lymphatic invasion, positive hormone receptors, and HER2/neu overexpression were 12.6%, 90.8%, and 2.1%, respectively. The median follow-up was 66.6 months (range: 1-126 months), and the overall survival and mastectomy-free rate reached 95.7% and 90%, respectively. Thirteen patients showed side effects; four recurrences were recorded, of which 50% were out-field relapses. The 5-year Kaplan-Meier probability of local relapses, mastectomy-free, and overall survival reached 97.5%, 100%, and 98%, respectively. This is the first 10-year report about the effect of IORT on Mexican women with EBC in the early stages. Strict adherence to the selection criteria in this study resulted in low rates of side effects, mortality, and local recurrences, demonstrating that IORT is an effective treatment alternative for patients with EBC. Studies with a longer follow-up period should be performed, as recurrences can occur in the long term.