ESTRO 2025 - Abstract Book

S306

Brachytherapy – Head & neck, skin, eye

ESTRO 2025

3519

Digital Poster Localized and Age-Specific Fractionation Schedules for Epidermoid and Basal Cell Carcinomas: A Retrospective Dosimetric Study Sergio Lozares 1,2 , Arantxa Campos 3 , Irene Carruesco 3 , Ana Galán 3 , Reyes Ibáñez 3 1 Medical Physics, Miguel Servet University Hospital, Zaragoza, Spain. 2 Radiology and Radiation Protection, University of Zaragoza, Zaragoza, Spain. 3 Radiation Oncology, Miguel Servet University Hospital, Zaragoza, Spain Purpose/Objective: This study aims to propose localized and age-specific radiotherapy fractionation schedules for epidermoid and basal cell carcinomas, treated with low-energy photons in a superficial therapy unit. The objective is to guide clinical decisions and promote treatment standardization for these common non-melanoma skin cancers. Material/Methods: Data were collected from 896 patients diagnosed with epidermoid or basal cell carcinoma and treated using low energy photon beams in a superficial therapy unit. Parameters analyzed included dose per fraction, total dose, number of sessions, biologically effective dose (BED), EQD2, patient age, and tumor localization. BED and EQD2 were calculated using an α/β ratio of 10 Gy for epidermoid carcinoma and 3 Gy for basal cell carcinoma. Results were stratified by tumor type, localization, and age group to identify optimal fractionation patterns. Epidermoid Carcinoma: Patients (n=303) received treatment localized to sites such as the abdomen, scalp, and external canthus. BED values ranged from 73.05 to 100 Gy. A hypofractionated regimen of 8 Gy/session (6 fractions) was common in patients >80 years, while younger patients (<70 years) were treated with 4 Gy/session (15 fractions), achieving BEDs of 80-100 Gy. Proposed schedules: 1. Elderly (>80 years): Hypofractionation (8 Gy/session, 6 fractions). Results: •

2. Middle-aged (70-80 years): Moderate hypofractionation (7 Gy/session, 8 fractions). 3. Younger (<70 years): Conventional fractionation (4 Gy/session, 15 fractions). • Basal Cell Carcinoma:

Patients (n=593) with lesions in areas like the forearm, scalp, and cheek were treated with BEDs of 56-86 Gy. Higher dose per session (8 Gy/session) was prevalent in elderly patients (>80 years) with small lesions, while younger patients required increased fractions to achieve equivalent BEDs. Proposed schedules: 1. Elderly (>80 years): Hypofractionation (8 Gy/session, 6 fractions).

2. Middle-aged (70-80 years): Moderate hypofractionation (5 Gy/session, 10 fractions). 3. Younger (<70 years): Conventional fractionation (4 Gy/session, 13 fractions).