ESTRO 2025 - Abstract Book

S480

Clinical - Breast

ESTRO 2025

Conclusion: SBRT is more effective than EBRT in delaying the change of systemic therapy in patients with oligoprogressive breast cancer, after controlling for molecular subtype and disease extent.

Keywords: SBRT, oligoprogression, breast cancer

1341

Digital Poster Dosimetry and early toxicities of the ACCEL dose fractionation for APBI from a tertiary institute Vrushab Rao, Mansi Munshi, Niraj Dhawale CyberKnife Radiosurgery and Radiation Oncology, Ruby Hall Clinic, Pune, India Purpose/Objective: The ACCEL protocol for Accelerated Partial Breast Irradiation (APBI) represents a promising approach in the management of early-stage breast cancer, offering a targeted radiation therapy option that reduces treatment time and minimizes exposure to critical structures. This study aims to analyze the dosimetric parameters and acute toxicities of the ACCEL protocol for APBI at our institution. Material/Methods: 16 consecutive patients selected using the ASTRO APBI criteria in 2024 and treated with the ACCEL dose fractionation (27 Gy in 5 fractions) were analyzed. All patients were planned with volumetric modulated arc therapy (VMAT). The dosimetric parameters studied included ipsilateral breast volume receiving 50% dose (V50%), ipsilateral breast volume receiving 95% of the prescribed dose (V95%), ipsilateral lung receiving 10% of the prescribed dose (V10%), ipsilateral lung receiving 30% of the prescribed dose (V30%), contralateral breast volume receiving 3% of the prescribed dose (V3%), heart dose according to the constraints mentioned by ACCEL, mean heart dose (MHD), mean lung dose (MLD), and acute skin toxicities. The results were compared to the ACCEL data. Results: 7 patients had right-sided breast cancer and 9 patients had left-sided breast cancer. The mean planning target volume (PTV) was 62.1cc (range - 36.75-79.15cc). The dosimetric data is mentioned in the table below.