A, Survival following locoregional recurrence according to head and neck primary tumor subsite. B, Survival following metastasis according to head and neck primary tumor subsite. C, Survival following isolated locoregional failure according to human papillomavirus (HPV) or p16 status. D, Survival following metastasis according to number of metastatic tumors. HPC indicates hypopharyngeal carcinoma; LC, laryngeal carcinoma; OCC, oral cavity carcinoma; and OPC, oropharyngeal carcinoma