The most frequent grade 3-4 adverse events were mucosal inflammation ( 25 [ 40 % ] of 62 patients in the chemoradiotherapy group vs 37 [ 42 % ] of 89 patients in the radiotherapy plus panitumumab group ) , dysphagia ( 20 [ 32 % ] vs 36 [ 40 % ] ) , and radiation skin injury ( seven [ 11 % ] vs 21 [ 24 % ] ) .