Abstract
Combined small-cell lung carcinoma (C-SCLC) is small-cell lung carcinoma (SCLC) with added non-small-cell morphology. We report a case of epidermal growth factor receptor (EGFR) mutation-positive C-SCLC in an 84-year-old patient with metastatic brain lesions who developed intrinsic resistance to osimertinib, a tyrosine kinase inhibitor (TKI). The patient was diagnosed with small-cell transformation of non-small-cell lung carcinoma (NSCLC) and received 6 cycles of dose-adjusted durvalumab with etoposide and carboplatin. In December 2021, the patient received the seventeenth cycle of maintenance durvalumab 19 months after diagnosis and showed continued treatment response and disease control. Comprehensive molecular profiling and repeated biopsies are recommended in NSCLC patients who progress on first-line EGFR-TKIs. Durvalumab in combination with chemotherapy appears to be beneficial for EGFR mutation-positive C-SCLC patients that are resistant to TKIs.