HPV Subanalysis
The vast majority of patients included in the study were with missing HPV status (78%). An additional analysis was conducted excluding all patients with missing HPV information to further explore the data. The machine learning models were redeveloped and retested using this new population. In all, 4,284 patients were included in the subset analysis. Full demographic information is detailed in Supplemental Table 1. Of note, primary treatment with surgical resection was slightly more common than primary treatment with radiation (60% vs. 40%). In Supplemental Table 2, the performance of the machine learning models is displayed. The decision forest again yielded the strongest model with an AUC of 75% (95% CI, 72% to 79%), accuracy of 72%, precision of 68%, and recall of 65%. The most important factor found by way of the PFI scores was patient clinical T- classification. This was closely followed by the same tumor descriptors including primary site of the cancer, clinical N- classification, and grade. The full results of the PFI analysis are displayed in Supplemental Table 3.