At baseline, 13 functional ALK mutations were identified (5 were previously unreported in the literature); at end of treatment, 3 new mutations (known resistance mutations) were seen (I1171N, I1171S, G1202R; n = 1 for each mutation). PFS > 3 months was seen in pts with baseline F1174V, L1196M, S1157F, R1231W, G1128A, G1269A or C1156F mutations, suggesting alectinib activity with these variants.