When do you consider using ALK targeted systemic therapy in lieu of WBRT or SRS for patients with metastatic ALK-positive NSCLC?

The development of crizotinib in ALK positive patients led to incredible control rates systemically, but as is now well known, less ability to control CNS disease. When crizotinib was the sole FDA approved ALK directed therapy, this led to the concept of "treatment beyond progression" such that pati...