S967
Clinical - Oligometastatic cancer
ESTRO 2026
progressive lesions. Multivariate Cox regression models were applied to identify predictors of oncological outcomes. Results: Eighty-seven patients were included, with a median age of 68 years (range: 43–87) and a median follow-up of 14 months. Adenocarcinoma was the predominant histology (75 cases, 86.2%), followed by squamous cell carcinoma (12 cases, 13.8%). PDRT was administered after first-line systemic therapy in 61 patients (70.1%). At the last assessment, 12 (13.8%) patients achieved complete response, 29 (33.3%) partial response, and 46 (52.9%) stable disease.The median EFS was 5 months (range: 1–48), with a one-year actuarial EFS rate of 52.1% (95% CI: 46.4–57.8%). Median time to next treatment (TTNT) was 8 months (range: 1–68), while median progression-free survival (PFS) was 5 months (range: 1–39).On multivariate analysis, both PDRT directed at the primary tumor (HR = 0.28, 95% CI: 0.12–0.66; p < 0.01) and a complete response prior to oligoprogression (HR = 0.31, 95% CI: 0.10–0.95; p = 0.04) were significantly associated with improved EFS. Conversely, use of chemotherapy (HR = 2.33, 95% CI: 1.21–4.48; p = 0.02) and larger CTV volumes (HR = 1.01, 95% CI: 1.0004–1.0111; p = 0.03) were associated with worse outcomes.
Digital Poster 1289 Progression-Directed Ablative Radiotherapy Improves Event-Free Survival in Oligoprogressive NSCLC Lorenzo De Sanctis 1 , Riccardo Ray Colciago 1 , Giulia Rossano 1 , Matteo Ferrari 1 , Matteo Mombelli 1 , Ilenia Manno 1 , Federica Ferrario 2 , Valeria Faccenda 3 , Denis Panizza 3 , Stefano Arcangeli 1,2 1 Medicine and Surgery Department, University of Milan Bicocca, Milan, Italy. 2 Radiation Oncology, Fondazione IRCCS San Gerardo Dei Tintori, Monza, Italy. 3 Medical Physics, Fondazione IRCCS San Gerardo Dei Tintori, Monza, Italy Purpose/Objective: To evaluate the efficacy of progression-directed radiation therapy (PDRT) in patients with oligoprogressive non-small cell lung cancer (NSCLC), focusing on disease progression and changes in systemic therapy. Material/Methods: From January 2020 to October 2025, a retrospective single-centre analysis was conducted at our Institution, including NSCLC patients treated with PDRT for oligoprogressive disease. Oligoprogression was defined as progression involving fewer than five extracranial lesions or up to a total intracranial disease volume of 14 cc, following an initial response to systemic treatment. The primary endpoint was event- free survival (EFS), defined as the occurrence of any of the following: change in systemic therapy, progression within six months, or development of more than three
Conclusion: PDRT effectively delayed oncological events, resulting in a median EFS of 5 months and postponing the initiation of a new systemic therapy by a median of 8 months. These findings suggest that PDRT may represent a viable therapeutic strategy for prolonging disease stability and deferring systemic treatment in oligoprogressive NSCLC. Larger, prospective studies with extended follow-up are warranted to confirm these results. Keywords: NSCLC, Oligoprogression, PDRT
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