hey there, new to the site. i too have stage iv lung cancer... i have the ALK-cdk6 mutation and i too am on xalkori too. was rushed to the hospital in july 2015... after 12 days and several surgeries i was informed that i had just joined the club no one wants to be a member of. i have my first pet/ct scan since july, on monday. nervous about the results already. i was never told/warned about xalkori's achilles' heel: It does not cross the blood-brain barrier. thanks for mentioning it, i will press for scans now. i had a brain mri in the hospital, but nothing since then. your post is encouraging.