EGFR and small cell lung carcinoma: For instance, most patients with EGFR mutations will eventually develop a progressive disease course within about 1 year of EGFR-TKI treatment because of the most common mechanism—development of acquired EGFR T790M mutation, and approximately 3–10% of acquired resistance to EGFR-TKIs is associated with histologic transformation to small cell lung cancer [33, 34].