Segmentation of the 18F-FDG PET/CT tumors was performed using the LIFEx software, generating the radiomic features. 
LIFEx
We used the Mann-Whitney test to select radiomic features associated with the clinical outcome (death), excluding the features highly correlated with each other with Spearman correlation. 
Spearman correlation
Subsequently, ROC curves and a Kaplan-Meier analysis were performed.  When we used the derived cut-off points from these ROC curves (12.76 for SUVpeak and 0.001 for GLRLM_LRLGE) in a Kaplan-Meier analysis, we can see two different groups (one with an overall survival probability of approximately 90% and the other with 30%). 
ROC curves
Subsequently, ROC curves and a Kaplan-Meier analysis were performed.  When we used the derived cut-off points from these ROC curves (12.76 for SUVpeak and 0.001 for GLRLM_LRLGE) in a Kaplan-Meier analysis, we can see two different groups (one with an overall survival probability of approximately 90% and the other with 30%). 
Kaplan-Meier analysis