S915
Clinical - Mixed sites & palliation
ESTRO 2026
regression models.
analysis, all the dosimetric variables were found to be reliable parameters to distinguish patients at low-risk from those at high-risk of G1-G3 RN. BrainV16(brain parenchyma excluding GTV) and brainV18 (brain parenchyma excluding or including GTV) were found to be the strongest predictors for G2-G3 RN. A statistically significant correlation (p=0.030) was found between overall survival and brainV12 (brain parenchyma + GTV). Conclusion: The results of this retrospective study showed that brainV18 (brain parenchyma ± GTV) was the best predictive parameter for the risk of G2-G3 RN and brainV12 value (brain parenchyma + GTV) is correlated with OS. Keywords: radiosurgery brain metastses Re-irradiation of Bone Metastases: clinical and dosimetric insights from a large retrospective series. Chiara Lorubbio 1 , Ilaria Repetti 1 , Federico Mastroleo 1,2 , Maria Giulia Vincini 1 , Mattia Zaffaroni 1 , Cristiana Iuliana Fodor 1 , Annamaria Ferrari 1 , Gaia Piperno 1 , Daniela Alterio 1 , Elena Rondi 1 , Stefania Comi 1 , Floriana Pansini 1 , Francesca Emiro 1 , Giulia Marvaso 1,2 , Barbara Alicja Jereczek-Fossa 1,2 1 Division of Radiation Oncology, IEO - European Institut of Oncology, Milan, Italy. 2 Department of Oncology and Hemato-oncology, University of Milan, Milan, Italy Digital Poster 4290
Results: The cohort had a median age of 65 years, with genitourinary (47.1%) and breast (35.5%) cancers being the most common primaries. Re-RT was primarily palliative (58.7%), using techniques such as IMRT, SBRT, 3D-CRT. The median time between initial RT and re-RT was 25 months, with a median cumulative BED of 148 Gy and EQD2 of 76 Gy. At a median follow-up of 20 months, 109 lesions progressed, with a median time to local failure of 9.5 months. Local progression rates at 1 and 2 years were 37.0% and 50.1%, respectively. Higher cumulative BED and EQD2 values were associated with better local control. Complete radiological response was seen in 45% of patients, and partial response in 27.5%. Median OS was 20 months, with 1- and 2-year OS rates of 60% and 47%. Median PFS was 9 months, with 1- and 2- year PFS rates of 43% and 31%. Tumor histology influenced outcomes, with breast and genitourinary cancers (mainly prostate) showing superior OS and PFS compared to lung or gastrointestinal cancers. Toxicity was low, with only 0.8% of patients experiencing grade ≥ 3 events. Common acute toxicities included mild pain flare. The most notable late toxicity was vertebral collapse or bone fracture (7% of patients), though no significant correlation to cumulative dose or treatment volume was observed (Figure 1).
Purpose/Objective: Re-irradiation (re-RT) for bone metastases is
increasingly used as patient survival improves, but the efficacy, safety, and optimal dosimetric parameters for re-RT are still under investigation. This study evaluates oncological outcomes, toxicity profiles, and dosimetric parameters in patients undergoing a second course of radiotherapy for previously treated bone lesions. Material/Methods: A retrospective analysis was conducted on 242 patients who received re-RT for bone metastases at the European Institute of Oncology (IEO) between 2011 and 2024. Patient’s chatacteristics are listed in Table 1. Primary endpoints included dosimetric evaluation and time to local failure, while secondary endpoints included overall survival (OS), progression- free survival (PFS), and toxicity assessment. The biologically effective dose (BED) and equivalent dose in 2 Gy fractions (EQD2) were calculated. Toxicity was graded using CTCAE. Statistical analysis was performed using Kaplan-Meier survival curves and Cox
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