Non‐small‐cell lung cancer with ERBB2 mutation in non‐tyrosine kinase domain benefits from pyrotinib: A case report

Tyrosine kinase domain (TKD) mutation and particularly exon 20 insertion mutations of erb‐b2 receptor tyrosine kinase 2 (ERBB2/HER2) have been extensively reported in non‐small cell lung cancer (NSCLC). Nevertheless, the clinical significance of non‐TKD mutations remains unknown. To date, no clinical trials have revealed that tyrosine kinase inhibitors are effective in NSCLC patients with non‐TKD ERBB2 mutations. Here we report a patient with advanced lung adenocarcinoma harboring non‐TKD mutation of ERBB2, S335C, without other actionable alterations benefited from pyrotinib. After first‐line treatment of pyrotinib monotherapy, a pan‐HER inhibitor, the patient achieved a durable partial response with good tolerance. This case powerfully illustrates that pyrotinib might be a promising first‐line treatment strategy for NSCLC patients with non‐TKD mutation of ERBB2.