Abstract
Treatment of advanced non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation with EGFR-tyrosine kinase inhibitors (EGFR-TKIs) can achieve good disease control, but it will inevitably produce drug resistance. About 3%-10% of the resistance mechanism is small cell transformation. Two cases of stage IV lung adenocarcinoma with EGFR mutation were reported and the disease was controlled after EGFR-TKIs treatment. In case 1, progression-free survival (PFS) before small cell carcinoma transformation was 16 months, and in case 2, PFS before small cell carcinoma transformation was 24 months. Subsequent biopsy after disease progression indicated a shift to small cell lung cancer. Case 1 PFS after small cell carcinoma transformation was 6 months, and case 2 PFS after small cell carcinoma transformation was 8 months, and overall survival (OS) was 36 months, which significantly prolonged the patient's survival. At the same time, the literature of such drug resistance mutations was reviewed. For patients with advanced NSCLC with sensitive mutations, it is necessary to conduct secondary histopathological tests after TKIs treatment resistance, and select subsequent treatment according to different resistance mechanisms for the whole course of disease management.
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