Successful long-term treatment of non–small cell lung cancer positive for RET rearrangement with pemetrexed

The discovery of RET rearrangement in non–small cell lung cancer (NSCLC) has prompted development of molecularly targeted therapy for such tumors, with several clinical trials being under way to evaluate the therapeutic effects of multitargeted tyrosine kinase inhibitors. The sensitivity of RET fusion–positive NSCLC to cytotoxic chemotherapy has remained unclear, however. We here report a case of NSCLC positive for the CCDC6-RET fusion gene that benefited from treatment with pemetrexed over a period of 30 months, suggesting that thymidylate synthase–targeted drugs such as pemetrexed may show efficacy for NSCLC harboring RET fusions.