ESTRO 2025 - Abstract Book

S1380

Clinical - Lung

ESTRO 2025

matching was performed with a 1:4 nearest neighbor matching algorithm without replacement, within a specified caliper distance of 0.2. PSM was based on sex, age (≤65 or >65 years), performance status (0 or 1-2), tobacco use, T and N stage. Results: Among the 209 included patients, 21 (10%) received tumor SBRT. The median age was 63.2 years (IQR 58.1-69.0). Most patients were male (n=143, 68.4%), had adenocarcinoma (n=124, 59.3%) and positive PDL1 (1-49%: n=80, 38.3%; >50%: n=65, 35.9%). Median NFRT dose was 66 Gy (range 60-74), mainly delivered by VMAT (n=65, 77.4%). Most frequent SBRT regimen was 50 Gy in 5 fractions (n=6; range 42.5-63.5 Gy, 3-5 fractions), usually delivered after mediastinal NFRT (n=11, 52.4%). After a median follow-up of 38 months, tumor SBRT was associated with longer PFS (median not reached vs 22.3 months; HR=0.46, p=0.047), a trend to longer OS (median not reached vs 45 months; HR=0.53, p=0.18) (Figure 1 A B). These results persisted after PSM (PFS: HR=0.39, p=0.03; OS: HR=0.42, p=0.08) (Figure 1 C-D) and in multivariate analysis of both overall and matched cohort (in PSM cohort : PFS=0.40, p=0.031; OS HR=0.45, p=0.10). Despite limited sample, post-NFRT SBRT tends to be associated with longer PFS (p=0.056) compared to standard PACIFIC regimen, without an increase in OS (p=0.17; Figure 2). No difference was observed between pre-NFRT SBRT and standard regimen (PFS p=0.24, OS p=0.61). Acute grade 3 toxicities were comparable, related to RT (14.3% vs 11.7%, p=0.78) or durvalumab (4.8% vs 13.3%, p=0.41), no grade 4-5 toxicity was reported.