Phase Iii Randomized Trial Of Standard Fractionation Radiotherapy (Sfx) With Concurrent Cisplatin (Cis) Versus Accelerated Fractionation Radiotherapy (Afx) With Panitumumab (Pmab) In Patients (Pts) With Locoregionally Advanced Squamous Cell Carcinoma Of The Head And Neck (La-Scchn): Ncic Clinical Trials Group Hn.6 Trial.