Individualized management strategies for advanced non‑small cell lung cancer with <i>EGFR</i> exon 19 deletion and L861Q compound mutations based on circulating tumor DNA monitoring: A case report

Epidermal growth factor receptor (EGFR) mutations are major oncogenic drivers in non-small cell lung cancer (NSCLC). These alterations, particularly prevalent in lung adenocarcinoma among the Chinese population, include the exon 19 deletion (19del), L858R point mutation and the less frequent L861Q variant. However, to the best of our knowledge, no standardized treatment regimen exists for patients harboring both common and rare EGFR mutations. The current study presents a case of advanced metastatic lung adenocarcinoma with concurrent EGFR 19del and L861Q mutations, managed with tyrosine kinase inhibitors targeting EGFR and dynamic plasma circulating tumor DNA (ctDNA) monitoring. The patient achieved a progression-free survival time of 11 months. Serial plasma ctDNA monitoring detected molecular progression, characterized by an increase in total ctDNA and a rising <i>EGFR</i> C797S allele fraction, prior to radiographic changes. The present case emphasized the importance of individualized management and the key role of ctDNA in real-time treatment monitoring, offering a potentially novel approach for precise disease evaluation in the future. Further research and the development of novel therapies are warranted to potentially improve outcomes in patients with advanced <i>EGFR</i>-mutated NSCLC.