Hi @stimey60, I hadn't had a chance to welcome you to Mayo Connect yet, and I'm glad that many members have commented on your post.
There are some types of lung cancer that are caused by mutating genes which are 'targetable' with medications, referred to as targeted therapies. When biopsies are performed the tissue/fluid is usually sent for biomarker testing. That test can identify if there is a gene mutation driving the cancer.
Tagrisso is a targeted therapy specific to EGFR mutated lung cancer.

I'm glad that you are starting to feel better, and that you found Mayo Connect.