Figure 1

Flow chart of head and neck squamous cell carcinoma patients enrolled in the study. FU=follow-up; *=these 15 patients are part of the 66 and 22 head and neck squamous cell carcinoma patients. The three groups of head and neck squamous cell carcinoma patients all belong to the Italian National Cancer Institute ‘Regina Elena’ cohort and were consecutively enrolled from 2007 to 2016.