ESTRO 2025 - Abstract Book

S471

Clinical - Breast

ESTRO 2025

Conclusion: Moderate hypofractionated PBT salvage reRT for LRR of BC is feasible,with acceptable rates of acute toxicities. A longer follow up is required to collect data on long term toxicity and clinical outcomes

Keywords: Protontherapy, reirradiation, hypofractionation

1138

Digital Poster Phase 3 Trial of Hypofractionated Radiotherapy for Breast Cancer: A Comparison of One-Week vs. Three Week Regimens at Kenyatta National Hospital CATHERINE N NYONGESA 1 , NJOKI P NJIRAINI 1 , Regina O Nanzia 1 , Daniel B Nyongesa 2 , Christine Wambui 3 1 CANCER TREATMENT CENTER, KENYATTA NATIONAL HOSPITAL, NAIROBI, Kenya. 2 KMTC, KMTC, NAIROBI, Kenya. 3 Centro de Estudios Biosanitarios, Centro de Estudios Biosanitarios, ONLINE, Spain Purpose/Objective: This study aims to evaluate the safety and effectiveness of a condensed adjuvant radiotherapy regimen, delivering five fractions over one week (26 Gy/5 fractions, "wiki Moja") compared to a three-week regimen (40 Gy/15 fractions). Conducted at the Cancer Treatment Center (CTC) of Kenyatta National Hospital (KNH), the trial seeks to determine potential differences in patient outcomes, treatment efficiency, and adverse effects between these two hypofractionated radiotherapy protocols for breast cancer patients. Material/Methods: This Phase 3 randomized non-inferiority trial includes adult participants with Stage I-III invasive breast carcinoma who have undergone surgery. Patients are randomly assigned to either the one-week or three-week regimen. Clinical outcomes, patient-reported experiences, and adverse events are tracked to compare toxicity levels and assess patient tolerance. Forty-seven patients were allocated to each treatment arm, with unblinded allocation and structured data collection on clinical metrics and toxicities. Results: Preliminary findings confirm that the one-week "wiki Moja" regimen is safe and well-tolerated by patients, showing substantial benefits in terms of cost savings, time efficiency, and reduced toxicity. This shorter regimen minimizes patient time commitments and enhances accessibility. They could reduce waiting time particularly for cases of triple-negative breast cancer (TNBC) and HER2-positive patients, who often require timely interventions. However, due to the limited follow-up period of 12 months, conclusions on loco-regional control remain inconclusive.