Overall, five of 23 patients (21.7%) met PFS3 (two partial response, three stable disease). Notably, among the 21 tumors analyzed, five of six patients (83.3%) with HER2 and/or ERBB3 alterations achieved PFS3 (PFS = 10.3, 7.0, 6.9, 6.3, and 5.0 months, respectively) versus none of 15 patients without alterations (P < .001). Three of four patients with HER2 amplification and three of three patients with ERBB3 somatic mutations (G284R, V104M, and R103G) met PFS3....Afatinib demonstrated significant activity in patients with platinum-refractory UC with HER2 or ERBB3 alterations.