Moderately hypofractionated radiation therapy for breast cancer: A Brazilian cohort study.

[BACKGROUND] Results from numerous clinical trials have led to a consensus that moderately hypofractionated radiation therapy is the ideal postoperative irradiation treatment plan in patients with breast cancer (BC). However, there are specific situations such as chest wall (with or without breast reconstruction) and regional node irradiation that still face obstacles in its widespread use. There is a lack of evidence supporting the use of moderately hypofractionated irradiation from the Latin American context. This study aims to describe the profile and clinical outcomes of patients treated with moderate hypofractionation for both early-stage (Stage I and II) and locally advanced BC (Stage III) regardless of the type of surgery in a Brazilian Oncology Center.

[METHODS] All patients with non-metastatic BC who were treated with moderately hypofractionated schedules of 40Gy in 15 fractions or 42.4Gy in 16 fractions between 2010 to 2019 at Hospital Sírio-Libanês, Brazil were retrospectively analyzed. The rates of local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS), distance recurrence-free survival (DRFS) and overall survival (OS) were estimated. Acute and late toxicity profiles were accessed for the entire cohort.

[FINDINGS] A total of 670 patients were included. The median age was 57 years and the median follow-up time was 31 months. Most of the patients had stage I and II breast cancer, and 81.6% underwent breast-conserving surgery. Of the 123 women who underwent mastectomy treatment, 29% ( = 37) had immediate reconstruction with implants and 28% ( = 35) with autologous tissue. Seventy-one per cent of the patients presented luminal subtype tumour and 84.3% received adjuvant hormonal therapy. Chemotherapy was administered to almost half of the patients and all 80 patients with Her-2 positive disease received trastuzumab-based systemic therapy. One-third of patients received regional node irradiation; boost was performed in 41.1% of treatments. The 5-year LRFS, RRFS, DRFS and OS was 95.6%, 97.6%,92.2% and 95.9%, respectively. Acute and late side effects profile were mild and only 2.9% of patients developed grade 3 dermatitis. Among patients with breast implants, 11.4% had capsular contracture.

[INTERPRETATION] In this Brazilian institution experience, moderately hypofractionated irradiation to the breast, chest wall (with or without breast reconstruction), and regional lymph nodes was safe and with an acceptable toxicity profile.

[FUNDING] None.