Abstract PS1-07-07: Assessment of Cutaneous Toxicity in Patients Treated with Ultra-Hypofractionated Radiotherapy in the Right Breast at the Pernambuco Cancer Hospital, Brazil

Abstract Background: Ultra-hypofractionated (UH) radiotherapy has emerged as a cost-effective and time-saving alternative for early breast cancer treatment. While randomized trials like FAST-Forward have demonstrated its safety and efficacy, real-world evidence in public healthcare settings lacking advanced radiotherapy technologies remains limited. Objective: To evaluate the degree of acute cutaneous toxicity in patients treated with ultra-hypofractionated radiotherapy (26 Gy in 5 fractions) for right-sided breast cancer in a Brazilian public hospital. Methods: A retrospective cross-sectional analytical study was conducted using medical records of 117 female patients treated between November 2021 and November 2023 at the Pernambuco Cancer Hospital. Eligible patients underwent adjuvant UH radiotherapy to the right breast. Exclusion criteria included incomplete data, treatment with conventional or moderately hypofractionated regimens, male sex, and left-sided tumors (due to cardiac exposure constraints without IMRT or DIBH). Skin toxicity was classified according to the Radiation Therapy Oncology Group (RTOG) scale. Statistical analysis included chi-square and Fisher's exact tests with a 5% significance threshold. Results: The mean age of patients was 59.9 years, with 80.3% over 50 years old and 51.3% having systemic arterial hypertension. Most tumors were invasive ductal carcinoma (76.1%) with luminal B (44.4%) and luminal A (37.6%) subtypes. Quadrantectomy was performed in 95.7%, with 38.5% receiving chemotherapy. Acute radiodermatitis was observed in 66.7% of patients: Grade 1 in 54.7%, Grade 2 in 9.4%, Grade 3 in only 2.6%, and no Grade 4 cases. A statistically significant association was found between hypertension and the presence of radiodermatitis (p=0.050), suggesting a potential link with underlying vascular changes or obesity, warranting further investigation. Conclusion: This study reinforces that ultra-hypofractionated radiotherapy is a safe and feasible treatment for right-sided breast cancer, even in public hospitals lacking advanced radiotherapy technologies. The acute toxicity profile was consistent with international trials, notably FAST-Forward, with a predominance of mild radiodermatitis and minimal severe events. These findings support the broader implementation of UH regimens in resource-limited settings to optimize treatment access and reduce patient burden. Citation Format: C. S. Vasconcelos, P. L. Quidute, M. Salgado, D. S. Viana, L. Torres, L. Mendonça, . Assessment of Cutaneous Toxicity in Patients Treated with Ultra-Hypofractionated Radiotherapy in the Right Breast at the Pernambuco Cancer Hospital, Brazil [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-07-07.