The most frequent grade 3-4 adverse events were dysphagia ( 17 [ 27 % ] of 63 patients in the chemoradiotherapy group vs 35 [ 40 % ] of 87 in the panitumumab plus chemoradiotherapy group ) , mucosal inflammation ( 15 [ 24 % ] vs 48 [ 55 % ] ) , and radiation skin injury ( eight [ 13 % ] vs 27 [ 31 % ] ) .