In patients who received at least one dose of study drug , the most frequent grade 3-4 adverse events were diarrhoea ( 47 [ 11 % ] patients in the dacomitinib group vs ten [ 2 % ] patients in the erlotinib group ) , rash ( 29 [ 7 % ] vs 12 [ 3 % ] ) , and stomatitis ( 15 [ 3 % ] vs two [ < 1 % ] ) .