ESTRO 2025 - Abstract Book

S512

Clinical - Breast

ESTRO 2025

was performed in selected cases. Data collected included patient demographics, tumor characteristics, treatment details, and acute and late toxicities.

Results: The median patient age was 55 years (range: 30–86). The majority of tumors were infiltrating ductal carcinomas (80%), with Luminal A being the most common molecular subtype (58.5%). Most patients presented with stage IA disease (61%), pT1c tumors (40%), and grade 2 histology (50%). Neoadjuvant chemotherapy was administered in 18.3% of patients, adjuvant chemotherapy in 23.5%, and hormonal therapy in 82.5%; 99% underwent surgery. The median radiotherapy dose to the whole breast was 30 Gy (range: 29– 33.6 Gy). Acute toxicities observed within six months of treatment were predominantly grade 1 (G1), with induration being the most frequent. Neoadjuvant chemotherapy was linked to higher rates of acute induration, while adjuvant chemotherapy was associated with increased acute and late hyperpigmentation. Late toxicities included G1 induration, edema, and hyperpigmentation. Conclusion: The FAST-Forward radiotherapy regimen, incorporating SIB and RNI, delivered over five daily fractions, demonstrated a favorable safety profile in early-stage breast cancer patients, with minimal acute and late toxicities. Larger-scale studies with extended follow-up periods are necessary to confirm these findings and evaluate long term clinical outcomes. Digital Poster Continuous positive airway pressure use in left-sided breast cancer radiotherapy: Understanding the anatomic rationale behind Zeineb Naimi 1 , Amal Riahi 1 , Azza Slim 2 , Raouia Ben Amor 1 , Awatef Hamdoun 1 , Ghada Bouguerra 1 , Rihab Haddad 1 , Raja Oueslati 1 , Lotfi Kochbati 1 1 Radiation Oncology Department, Abderrahmen Mami Hospital, Ariana, Tunisia. 2 Pneumology Department, Abderrahmen Mami Hospital, Ariana, Tunisia Purpose/Objective: This study aimed to assess the anatomic impact of using continuous positive airway pressure (CPAP) in left sided breast cancer radiotherapy with regards to cardiac-thoracic anatomy. Material/Methods: Fifty consecutive patients with left-sided breast cancer, referred for adjuvant hypofractionated radiotherapy, were prospectively included in this study. Patients were trained to breath with CPAP device using a facial mask, for 30 minutes under a maximum tolerable pressure of 10-15 cmH2O. Each patient underwent simulation CT twice: with free breathing (FB) and with CPAP. Treatment plans were generated for both CTs using a 3D conformal technique. The following anatomic parameters were assessed on both simulation CTs: Distance SC = distance from the sternal notch to the superior border of the heart contour, ContactHeart = largest sagittal heart contact with the thoracic wall, Cardiac volume, Ipsilateral Lung volume, volumes of the heart, left ventricle and left anterior descending artery included in tangential fields (respectively HeartTg , LVTg and LADTg) . Anatomic parameters were statistically compared between the two simulation CTs using the t student test. Results: Fifty-two percent of patients underwent radiotherapy to the whole breast and 48% to the chest wall. Regional lymph nodes, including internal mammary chain, were irradiated in 64%. Compared with FB, CPAP significantly increased Keywords: FF, Simultaneous Boost, Regional Nodal Irradiation 2141