Fig. 2.

Validation of the radioresistance (RadR) score in human papillomavirus (HPV)-negative head and neck squamous cell carcinoma (HNSCC). The RadR score, defined by the gene expression-based enrichment score of 13 genes, was computed in 44 paired HNSCC and normal mucosa (GSE6631) (a), 5 HNSCC cell lines (GSE21644) (b), 59 pancancer cell lines (NCI-60) (c), and 63 HPV-negative HNSCC (GSE39366) (d). The RadR score was compared between normal and tumor samples (a); between HNSCC cell lines (ranked from left to right according to their increasing intrinsic radioresistance as previously defined [23]) (b); and between three groups of cancer cell lines from NCI60, defined by their survival fraction at 2 Gy (SF2) as previously described [30] (c). We divided the 63 patients from GSE39366 into two groups according to treatment as (1) surgery + adjuvant radiotherapy (with or without chemotherapy) and (2) surgery (with or without adjuvant chemotherapy). Survival distributions were estimated in each group using the Kaplan–Meier method and compared with the log‐rank test between subgroups of patients defined by the median RadR score (low versus high RadR score)