Long survival of two cases of transformation of lung adenocarcinoma to small cell lung cancer

HAO Lizheng; XIA Xiuling; SUN Li; WANG Lihong; YU Haiyan; FAN Zaiwen; WANG Yu

doi:10.3969/j.issn.2097-1753.2025.05.023

Abstract：Objective To deeply explore the clinical pathological features, genetic changes, and treatment patterns of lung adenocarcinoma transforming into small cell lung cancer (SCLC), to provide evidence for optimizing the clinical management of these patients. Methods We retrospectively analyzed the clinical data of two patients with lung adenocarcinoma transforming into SCLC, carefully reviewed their diagnostic process, pathology, gene detection results, treatment plans, and survival outcomes, and conducted a comprehensive analysis by systematically reviewing relevant literature at home and abroad. Results Both patients were male non-smokers, initially diagnosed with lung adenocarcinoma, and developed SCLC transformation during the extensive stage. Gene testing showed that case 1 had rare mutations in EGFR exon 18 (G719S) and exon 20 (S768I), as well as TP53 mutation. In three dynamic tests, the mutation frequencies of EGFR and TP53 increased after SCLC transformation. Case 2 had an EGFR exon 19 deletion (E746_A750del). Three tests from July 2019 to June 2021 showed that the EGFR mutation frequency continuously increased, consistent with the slow progression of pulmonary lesions. Both long-term survival patients experienced SCLC transformation after treatment with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs). After chemotherapy, radiotherapy, and long-course immunotherapy, both patients had overall survival times exceeding 50 months. Conclusion Patients with lung adenocarcinoma transforming into SCLC have specific clinical and molecular characteristics. The combination of immunotherapy and chemotherapy may offer an effective treatment option for these patients, and further research is needed to verify their long-term efficacy and molecular mechanisms.