A case of CD74‐ROS1‐positive lung adenocarcinoma diagnosed by next‐generation sequencing achieved long‐term survival with pemetrexed regimens

Previously, cytotoxic drugs were the only option for patients with non‐small cell lung cancer (NSCLC) and the prognosis was poor. However, molecularly targeted therapies and immune checkpoint inhibitors represent a breakthrough in the treatment of advanced NSCLC and have improved survival rates. In addition, advances in next‐generation sequencing (NGS) have revealed the landscape of genomic alterations in patients with different cancers, aiding in the development of new molecularly targeted drugs. The patient reported here was a 54‐year‐old woman with left lower lung adenocarcinoma. The lung cancer was staged as T2aN3M1a stageIVA 11 years ago. She had received seven regimens of chemotherapy for 11 years. Among these, pemetrexed (PEM) regimens particularly showed long‐term effects totaling more than 5 years. We performed NGS after disease progression of the seventh treatment. NGS revealed CD74‐ROS1 fusion and she was treated with entrectinib. She has been taking entrectinib for over 20 months now. Herein, we report a rare case of CD74‐ROS1‐positive lung adenocarcinoma diagnosed by NGS that achieved long‐term survival with cytotoxic drugs, especially PEM regimens. In patients showing favorable clinical response to PEM regimens, physicians should consider testing for ROS1/ALK rearrangement.