ESTRO 2025 - Abstract Book

S582

Clinical - Breast

ESTRO 2025

2. Yamamoto M, Serizawa T, Nagano O, et al (2020) Three-institution study on applicability of initial brain metastasis velocity for breast cancer brain metastasis patients undergoing stereotactic radiosurgery. J Neurooncol 147:177–184. https://doi.org/10.1007/s11060-020-03412-z

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Digital Poster IORT (Intra Operative RadioTherapy) full dose of 21 Gy in breast cancer: single-institutional retrospective analysis in 1011 patients. Laura Maffioletti 1 , Elisabetta Vitali 1 , Giulia Rinaldi 1 , Micaela Motta 1 , Angelo Di Naro 1 , Miguel Espindola 2 , Maurizio Giovanni Agostino Portaluri 1 1 Division of Radiotherapy, ASST Papa Giovanni XXIII, Bergamo, Italy. 2 Radiotherapy, Centro Mèdico Nacional Siglo XXI IMSS, Mexico City, Mexico Purpose/Objective: IORT (Intra Operative RadioTherapy) 21 Gy in breast cancer: single-institutional retrospective analysis in 1011 patients and reconfirmation of the indication in well-selected cases. Material/Methods: From 2006 to 2024 were treated 1011 patients with IORT on the surgical bed with a dose of 21 Gy in a single fraction at the isodose of 90% of 10 MeV electrons. Until 2017 the enrollment criteria were: post-menopausal status, any grade of differentiation G1, G2 or G3, infiltrating carcinoma of hystology ductal, lobular or even carcinoma in situ, size < 30 mm, ER+/-, PgR+/-, Ki67 < 25% and Her2 negative hystotype. Since 2017 we have been enrolling patients excluding the hystologies lobular infiltrating and intraductal carcinoma, the grade of differentiation G3 and Ki67 > 20% and also we have limited the enrollment of patients with dimension of T > 20 mm. All patients underwent annual radiotherapy follow-up for an average of 10.7 years (range 1-18.5 years), all the radiological images of the mammograms were evaluated for the presence of liponecrosis and palpable clinical fibrosis was reported. Results: Overall survival was 18,46 years. OS according to Ki67 > or < 20% and to T size were statistically significant (p<0.001 for both of all, Fig. 1). Also local recurrence-free survival according to T size > o< of 15 mm was statistically significant (p<0.004, Fig. 2). The total number of mastectomy was 100: 61% occurred in T size > 15 mm, 39% in < 15 mm. Radiological liponecrosis was recorded in 163 (16.3%) patients. The cosmetic data was aggreable with G2/G3 fibrosis reported in only 19 patients (1.88%).