Table 2 Algorithm of the stepwise statistical analysis perfomed on the discovery and validation datasets

Step 1: 2-Gene Models to Predict Immunotherapy Response and Survival

 CORExpress 1.1 regression analysis software for high-dimensional data

 Train 2-gene models with pre-treatment Discovery dataset N = 210

 Test 2-gene models with pre-treatment Validation dataset N = 150

 Over 260 2-gene synergistic pre-treatment models trained and validated

Step 2: Larger Gene Models to More Accurately Predict Response and Survival

 Include only genes validated in 2-gene models from Step 1

 Optimize model coefficients using CORExpress 1.1 software

 Train optimized models with pre-treatment Discovery dataset N = 210

 Test optimized models with pre-treatment Validation dataset N = 150

Step 3: Finalize 15-Gene Model to Predict Response and Survival

 Optimal 15-gene pre-treatment model selected from Step 3

 Use MedCalc version 17 software for ROC and p-value analysis

 Test 15-gene model with pre-treatment Discovery dataset N = 210

 Test 15-gene model with pre-treatment validation dataset N = 150

Step 4: Test Pre-treatment 15-Gene Model with Post-Treatment Datasets

 15-gene pre-treatment response and survival model from Step 3

 Use MedCalc version 17 software for ROC and p-value analysis

 Test 15-gene model with post-treatment Discovery dataset N = 210

 Test 15-gene model with post-treatment Validation dataset N = 150