Successful targeting of the NRG1 fusion reveals durable response to afatinib in lung adenocarcinoma: a case report

The treatments for advanced non-small cell lung cancer (NSCLC) patients have been improved by developing tyrosine kinase inhibitors (TKIs) as targeted therapies. Oncogenic gene fusions resulting from structural DNA rearrangements have been proposed as a unique class of oncogenic drivers and therapeutic targets. Currently approved TKIs mainly focused on a few well-known fusion genes such as anaplastic lymphoma kinase (ALK) and ROS proto-oncogene 1 (ROS1). Fusions involving neuregulin 1 gene (NRG1) have been recently described in a small portion of solid tumors as actionable oncogenic drivers, leading to the activation of the erythroblastic leukemia viral oncogene homolog (ErbB)-mediated pathway. Therefore, gene fusions containing NRG1 could serve as a therapeutic candidate for ErbB-targeted treatment. In the present study, we report a lung adenocarcinoma patient harboring the CD74-NRG1 fusion, which was identified by next-generation sequencing (NGS). The patient received the irreversible pan-ErbB inhibitor, afatinib, as first-line treatment and showed a significant treatment response with a progression-free survival of 8 months. After progressive disease (PD), the second NGS did not identify novel genetic alterations that emerged after afatinib resistance. Our case supports the use of ErbB-targeted treatment for NRG1 fusion-positive NSCLC. Further studies are warranted to understand treatment effects and acquired resistance of afatinib in NGR1 fusion-positive patients.