Prolonged survival after small-cell transformation of EGFR-mutant lung adenocarcinoma: a case report

Transformed small cell lung cancer (T-SCLC) is most commonly observed in EGFR-mutant lung adenocarcinoma and represents an important mechanism of acquired resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs). Its reported clinical incidence is approximately 3%-10%. Patients with T-SCLC often experience rapid disease progression and poor overall prognosis, and no established standard treatment regimen is currently available. We report a case of advanced EGFR-mutant lung adenocarcinoma with RB1 , TP53 , and BRCA2 co-mutations that underwent small-cell transformation during treatment. Small-cell transformation was detected through close surveillance and confirmed by repeat biopsy. The patient subsequently received individualized multimodal therapy, including chemotherapy, targeted therapy, and local radiotherapy, and remained alive 43 months after the initial diagnosis.