S347
Clinical - Breast
ESTRO 2026
MFS beyond 60 months. Conclusion:
Digital Poster 5036 Outcomes of definitive radiotherapy in patients with unresectable breast cancer Donata Gräupner 1 , Marcin Kubeczko 2 , Roland Kulik 3 , Dorota Gabry ś 1 1 Radiotherapy Department, Maria Sklodowska - Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland. 2 Breast Cancer Center, Maria Sklodowska - Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland. 3 Radiotherapy Planning Department, Maria Sklodowska - Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Poland Purpose/Objective: Radiotherapy is an important treatment option for patients with locally advanced breast cancer who are not eligible for surgery due to advancement of the disease, comorbidities or lack of consent. The aim of our study was to evaluate treatment outcomes in such patients. Material/Methods: For our retrospective analysis we selected group of 61 breast cancer patients who were treated in our center between 2013 and 2021 with simultaneous integrated boost (SIB) in 30 fractions for unresected breast cancer. Doses were individualized according to the stage of the disease. The regional lymph nodes received 49.8–60 Gy, df 1.66–2 Gy, the whole breast 50-70 Gy, metastatic lymph nodes and breast tumour received 60–70 Gy, df 2–2.33 Gy. Majority of patients (75%) presented with clinical stage IIIB of the disease. Among them, 62.3% were HR+/HER2–, 16.4% HER2– positive, 16.4% TNBC. 26 patients underwent mastectomy after radiotherapy. Results: The median follow-up was 37.6 months (range 7.1– 154.7). The 5-year RFS was 77.3% (95%CI, 57.7–88.6) in the RT-only group versus 80.6% (95%CI, 54.2–92.7) p=0.45, in the post-RT mastectomy group. Five-year MFS was 69.4% (95%CI, 50.3–82.3) in the RT-only group versus 38.5% (95%CI, 18.7–58.1; p=0.17) in the post-RT mastectomy group. Five-year DFS was 60.1% (95%CI, 41.1–74.8) in the RT-only group versus 38.6% (95%CI, 18.7–58.2; p=0.56) in the post-RT mastectomy group. Subtype-specific analysis demonstrated excellent 5-year RFS in HR+/HER2– disease (83.1%, 95%CI, 63.3–92.8) and unexpectedly favorable outcomes in TNBC (85.7%, 95%CI, 33.4–97.9). In contrast, the HER2-positive subtype was associated with poorer prognosis and remained an independent predictor of relapse (HR 5.2, 95%CI, 1.32–20.8). Despite encouraging RFS rates, 5-year MFS was 40.5% (95%CI, 10.0–70.1) in TNBC compared with 66.9% (95%CI, 47.8– 80.3) in HR+/HER2– disease. Furthermore, no patients with HER2-positive BC were observed to have RFS or
Definitive radical radiotherapy provides meaningful local control in patients with unresectable breast cancer, including those who do not proceed to surgery. Comparable outcomes between the RT-only and post-RT mastectomy groups support the role of RT as an effective definitive option in non-surgical candidates. RT achieves very good local control even in aggressive breast cancer subtypes; however, due to their high metastatic potential, improved systemic treatment strategies are urgently needed. Further studies are warranted to refine patient selection and integrate advanced RT techniques with modern systemic therapies. Keywords: inoperable, SIB Comparative evaluation of 18F-Fluoroestradiol and 18F-FDG PET/CT in the management of hormone- receptor positive breast cancers Monica Emilia Chirila 1,2 , Sandrine Parisse Dimartino 3 , Arnaud Coulomb 4 , Adelina Brezae 4 , Gabriel Kacso 1,2 , Waisse Waissi 4 1 Radiotherapy-oncology, University of Medicine and Pharmacy Iuliu Hatieganu, Cluj-Napoca, Romania. 2 Radiation oncology, Amethyst Radiotherapy Centre, Cluj-Napoca, Romania. 3 Nuclear Medicine, Centrer Leon Berard, Lyon, France. 4 Radiation oncology, Centre Leon Berard, Lyon, France Digital Poster 5063 Purpose/Objective: Estrogen Receptor-Targeted Positron Emission Tomography Imaging with 16 α -18F-Fluoro-17 β - Fluoroestradiol (FES-PET) represents a new option for breast cancer (BC) patients. The study aimed to compare the clinical impact of using FES-PET and fluorodeoxyglucose F18 (FDG-PET) in selected cases. Material/Methods: Patients with a confirmed BC who underwent FDG and FES-PET imaging in the Nuclear Medicine Department of Centre Leon Berard from October 2022 to July 2025 were included. Clinical data were retrospectively collected. The results and impact of both investigations were analysed using descriptive Thirty-four patients matched the inclusion criteria. The median age at the time of FES PET was 65 (range 36 - 84). The most frequent types were lobular cancer (N=18; 52.9%) and ductal cancer (N=13; 38.2%). Hormone receptor positivity was documented at diagnosis in 31 patients (91.2%); most had HER2- negative tumours (N=30; 88.2%) and grade 2 SBR (N=24; 70.6%). Nine patients (26.5%) were metastatic statistics. Results:
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