Patients with stage III and IV head and neck squamous cell carcinoma treated on phase I and II chemoradiation trials with @-Gy radiation combined with tirapazamine/cisplatin or cisplatin/fluorouracil ( @FU ) , hypoxic imaging using -LSB- @F -RSB- - misonidazole positron emission tomography and known HPV status ( by p@ immunohistochemistry ) were included in this sub-study .