ALK-rearranged adenocarcinoma transformed to small-cell lung cancer: a new entity with specific prognosis and treatment?

Driving molecular mutations such as rearrangement of ALK and EGFR mutation is present in 5-10% of non-small-cell lung cancer. Tyrosine kinase inhibitors have shown good efficacy and thus become the standard of care. However, tumors have developed several resistance mechanisms against tyrosine kinase inhibitors, including transformation to small-cell lung carcinoma (SCLC). Transformation to SCLC after administration of anti-EGFR in EGFR-mutated adenocarcinoma has been well documented. Similarly, it appears that the same transformation happens in ALK-rearranged adenocarcinoma after the use of anti-ALK. In fact, to date eight cases have been reported in the literature. We aimed in this paper to focus on the characteristics, prognosis and treatment of these transformed SCLC.