Characteristic Comparison Hazard Ratio 95% CI P-Value Age at Diagnosis Per Year 1.004 0.99, 1.02 0.52 Baseline PET SUV Per Unit* 1.01 0.99, 1.02 0.23 Entropy Per Unit 0.94 0.76, 1.18 0.61 Performance status Per Unit 0.996 0.98, 1.01 0.6 Tumor Histology SCC vs. Adeno 0.75 0.52, 1.07 0.11 Tumor Length Per Unit 0.97 0.92, 1.02 0.25 Induction Chemo Yes vs. No 0.88 0.67, 1.16 0.37 Path Response Yes vs. No 1.27 0.30, 5.40 0.74 Tumor Grade Poor  vs. Well/Moderate 1.34 1.03, 1.73 0.03 Radiation Modality IMRT vs. 3D-CRT 0.73 0.55, 0.97 0.03 Protons vs. 3D-CRT 0.64 0.42, 0.97 0.03 Surgery Yes vs. No 0.34 0.22, 0.53 <0.0001 Overall Clinical Stage 3-4a vs. 1-2 1.75 1.29, 2.36 0.0003 Image-Derived Score Per Unit 1.61 1.13, 2.29 0.009

Table 4: Multivariate analysis of potential predictors of overall survival outcomes. Abbreviations: CI, confidence interval; PET, positron emission tomography; SUV, standardized uptake value; IMRT: Intensity-Modulated Radiation Therapy; 3D-CRT: Three-Dimensional Conformal Radiation Therapy. *Note baseline PET SUV was also analyzed as a dichotomized variable (using a clinical cutoff of SUV ≤ 2 vs. >2, and a median cutoff of SUV ≤ 10 vs. >10) in our multivariate model and its p-value for predicting OS remained >0.05.