Performing a re-biopsy for comprehensive genetic testing, and excluding small cell lung cancer transformation (a phenomenon observed in roughly 5% of EGFR TKI-resistant tumors), represents an optimal procedural step.402 If a new target arises, such as ALK or EGFRT790M mutation in patients with resistance to EGFR TKIs, one proceeds with the cycle of first-line therapy. Here, EGFR is linked to small cell lung carcinoma.