Abstract
BACKGROUND: Stereotactic body radiation therapy (SBRT) is an effective treatment for pulmonary oligometastases. Understanding the temporal evolution of computed tomography (CT) imaging features post-SBRT is crucial for optimizing patient management and improving prognostic outcomes. This study aimed to characterize the CT imaging evolution of pulmonary oligometastatic nodules following SBRT and evaluate the prognostic value of early tumor response for local control. METHODS: This multicenter retrospective study analyzed 246 pulmonary oligometastatic nodules in 191 patients treated with SBRT. We evaluated clinical characteristics, biologically effective dose (BED10), and CT imaging features, categorized by recurrence within 2 years. Tumor response at 1-month follow-up was classified as favorable [partial response (PR) or complete response (CR)] or bad [stable disease (SD) or progressive disease (PD)]. Statistical analyses included t-tests, Chi-squared tests, and Kaplan-Meier analysis. RESULTS: Significant predictors of non-recurrence included tumor diameter ≤20 mm (P<0.001), BED10 ≥100 Gy (P=0.022), and favorable early tumor response (P=0.001). The 2-year local control rate was 87.8% overall, 95.0% for nodules with a favorable early response, and 81.1% for those with a bad response. CT imaging showed that non-recurrent nodules typically exhibit early significant shrinkage, transient loose consolidation with ground-glass opacity (GGO), and eventual stable fibrosis, whereas recurrent nodules progress to mass-like consolidation. CONCLUSIONS: Favorable early response on 1-month follow-up CT, tumor diameter ≤20 mm, and BED10 ≥100 Gy are strong predictors of local control. Integrating early CT-based assessment into routine follow-up may improve recurrence detection and guide timely intervention.