Purpose-To investigate whether imaging features from pre-treatment planning CT scans are associated with overall survival (OS), recurrence-free survival (RFS), and loco-regional recurrence-free survival (LR-RFS) after stereotactic body radiotherapy (SBRT) among non-smallcell lung cancer (NSCLC) patients. Patients and methods-A total of 92 patients (median age: 73 years) with stage I or IIA NSCLC were qualified for this study. A total dose of 50 Gy in 5 fractions was the standard treatment.

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... es clinical characteristics, 24 "semantic" image features were manually scored based on a point scale (up to 5) and 219 computer-derived "radiomic" features were extracted based on whole tumor segmentation. Statistical analysis was performed using Cox proportional hazards model and Harrell's C-index, and the robustness of final prognostic model was assessed using ten-fold cross validation by dichotomizing patients according to the survival or recurrence status at 24 months. Results-Two-year OS, RFS and LR-RFS were 69.95%, 41.3% and 51.85%, respectively. There was an improvement of Harrell's C-index when adding imaging features to a clinical model. The model for OS contained the Eastern Cooperative Oncology Group (ECOG) performance status (Hazard Ratio [HR] = 2.78, 95% Confidence Interval [CI]: 1.37 -5.65), pleural retraction (HR = 0.27, 95% CI: 0.08 -0.92), F2 (short axis × longest diameter, HR = 1.72, 95% CI: 1.21 -2.44) and F186 (Hist-Energy-L1, HR = 1.27, 95% CI: 1.00 -1.61); The prognostic model for RFS contained vessel attachment (HR = 2.13, 95% CI: 1.24 -3.64) and F2 (HR = 1.69, 95% CI: 1.33 -2.15); and the model for LR-RFS contained the ECOG performance status (HR = 2.01, 95% CI: 1.12 -3.60) and F2 (HR = 1.67, 95% CI: 1.29 -2.18). Conclusions-Imaging features derived from planning CT demonstrate prognostic value for recurrence following SBRT treatment, and might be helpful in patient stratification.