The present study describes the case of a 48-year-old man who was diagnosed with lung adenocarcinoma with an epidermal growth factor receptor (EGFR) 21 L858R mutation. The patient received surgery and adjuvant chemotherapy. When multiple lung metastases appeared, icotinib was administered. Following resistance to icotinib, biopsy by endobroncheal ultrasonography for a right lung hilar lymph node revealed transformation to a neuroendocrine morphology. Neuron-specific enolase (NSE) levels were elevated, accompanied with disease progression following transformation to the neuroendocrine morphology. The post-operative and biopsy specimens were analyzed for 416 genes using next-generation sequencing, and phosphatidylinositol-3-kinase catalytic α mutation and retinoblastoma loss were evident. Five cycles of etoposide combined with cisplatin were administered and a partial response was achieved. The disease progressed again accompanied with an elevated NSE level, and bronchoscopy examination revealed small cell lung cancer (SCLC) after 3 months. The patient received chemotherapy consisting of irinotecan combined with carboplatin for two cycles and achieved stable disease. Overall, a secondary biopsy is important for the evaluation of genetic and histological changes and the selection of an appropriate treatment following tyrosine kinase inhibitor (TKI) resistance, and NSE may be useful for the early detection of SCLC transformation in cases that are resistant to EGFR-TKI therapy.
Keywords: adenocarcinoma; resistance; small cell lung cancer; transformation; tyrosine kinase inhibitor.