ESTRO 2025 - Abstract Book

S1474

Clinical – Mixed sites & palliation

ESTRO 2025

849

Digital Poster Predictive factors of response in lung metastases treated by SBRT from colon rectal cancer Donatella Caivano 1,2 , Paolo Bonome 3 , Donato Pezzulla 3 , Vitaliana De Sanctis 4 , Maurizio Valeriani 4 , Daniela Musio 2 , Mattia Falchetto Osti 1,4 1 Department of Medical and Surgical Sciences and Translational Medicine, Traslational Medicine and Oncology, Faculty of Medicine and Psycology, Sapienza University of Rome, Rome, Italy. 2 Department of Radiation Oncology, San Giovanni Addolorata Hospital, Rome, Italy. 3 Radiation Oncology Unit, Gemelli Molise Hospital - Università Cattolica del Sacro Cuore, Campobasso, Italy. 4 Department of Radiation Oncology, Sant’ Andrea Hospital, Sapienza University of Rome, Rome, Italy Purpose/Objective: To assess predictive factors of response in patients with lung metastases from primary colorectal cancer (CRC) treated by SBRT Material/Methods: This is a retrospective, single-centre study. Inclusion criteria are as follows: documented histological confirmation of CRC in the primary tumour, Karnofsky performance status > 60 and age >18 years. Results: From 2008 to 2023, we treated 149 lung metastases in 87 patients with colorectal cancer. We had 23 synchronous and 126 metachronous metastases. Using a simplified classification of oligometastatic disease, we observed 6% synchronous metastases, 38% oligorecurrent, 51% oligoprogressive and 5% oligopersistent lesions. The medium PTV volume was 16.74 cc. Single fractions were administered in 78 (52%) and multiple fractions in 71 (48%). The most common schedule was 30 Gy in single fractions. The medium BED (10) of SBRT was 113.04 Gy (range, 48-180 Gy). The LC rates at 1, 3 and 5 years were 74%, 62% and 55% respectively. In UVA, small GTV and diameter, high BED and EQD2, and age < 70 years were positive predictors of response. MVA confirmed diameter and EQD2. The PFS rates at 1, 3 and 5 years were 34%, 16% and 12% respectively. In UVA, good ECOG was a positive predictor of response, confirmed in MVA. The rates of PMD at 1, 3 and 5 years were 74%, 60% and 40% respectively. In UVA, high BED (10), small diameter, good ECOG and shorter time from first metastasis and SBRT were positively correlated with PMD. MVA confirmed diameter and time from first metastasis and SBRT. The rates of CSS at 1, 3 and 5 years were 81%, 37% and 16% respectively. Small GTV volume and diameter, high BED (10), good ECOG and oligometastatic disease classification type (worst results for oligoprogressive lesions) were correlated with CSS; at MVA, BED(10) and ECOG were confirmed. The OS rates at 1, 3 and 5 years were 78%, 35% and 16%, respectively. A high BED(10), a small diameter, a good ECOG, the primary site (better results for colorectal cancer) and the type of classification of oligometastatic disease (worst results for oligoprogressive lesions) were correlated with OS; at MVA, BED, diameter, ECOG and primary site were confirmed.