ESTRO 2025 - Abstract Book

S1494

Clinical – Mixed sites & palliation

ESTRO 2025

[2] Parfrey PS, Griffiths SM, Barrett BJ, Paul MD, Genge M, Withers J, et al. Contrast material-induced renal failure in patients with diabetes mellitus, renal insufficiency, or both. A prospective controlled study. N Engl J Med 1989;320:143 – 9. https://doi.org/10.1056/NEJM198901193200303.

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Digital Poster Comparative Outcomes of 0-7-21 and 20 Gy in 5 Fractions Palliative Radiotherapy Regimens for Breast Cancer: A Multicenter Study Majd Alotaibi 1 , Hanadi Habibullah 1 , Hatim Almarzouki 2,3 1 Radiation Oncology, King Faisal Specialist Hospital and Research Centre, Jeddah, Saudi Arabia. 2 Radiation Oncology, King Abdulaziz University, Jeddah, Saudi Arabia. 3 Radiation Oncology, Dr. Soliman Fakeeh Hospital, Jeddah, Saudi Arabia Purpose/Objective: To compare the efficacy, in terms of symptom control, radiological reduction in mass size, and toxicity profiles of the 0-7-21 palliative radiotherapy regimen compared to the 20 Gy in 5 fractions regimen for advanced breast cancer. This is the first study assessing the 0-7-21 regimen in palliating breast tumors, contributing unique insights into its clinical effectiveness and safety profile. Material/Methods: A retrospective multicenter study included 30 patients with advanced breast cancer treated with either the 0-7-21 regimen (three fractions over 21 days with dose per fraction 7-8Gy) or 20 Gy in 5 fractions between January 2020 and September 2024. Outcomes measured were symptom control, radiological mass size reduction, and treatment related toxicities graded using RTOG 1 criteria. Statistical analysis included chi- square and Fisher’s exact tests for categorical variables, independent t-tests for continuous variables, and PFS, defined as the time from treatment completion to disease progression or death, analyzed using Kaplan-Meier curves. Results: Patients had a mean age of 55.1±12 years, with invasive ductal carcinoma being the predominant histology (93.3%). Most patients had stage IV disease, with HR+ Her-2 negative (43.3%) and triple-negative (40%) receptor statuses. Among the 30 patients included in the study, 28 received palliative radiotherapy for a mass in the breast or chest wall, while 1 patient was treated for a supraclavicular mass and another for a pectoral lymph node mass. Complete symptom control was observed in 26.7% of patients treated with the 0-7-21 regimen versus 6.7% in the 20 Gy group, although this difference was not statistically significant (p=0.278). Radiological mass reduction was more frequent in the 0-7-21 group (88.9% vs. 57.1%, p=0.124). The mean reduction in mass size was 66.75±31.17% for the 0-7-21 group and 72.0±20.61% for the 20 Gy group (p=0.711). There was no statistically significant difference in PFS between the groups (p=0.444). Toxicity was mild in both groups, with one Grade III dermatitis case reported in the 0-7-21 group.