Case Report: Furmonertinib dose escalation in heavily pretreated EGFR-mutant lung adenocarcinoma with diffuse brain metastases.

Furmonertinib, a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, has demonstrated systemic and central nervous system (CNS) antitumor activity in patients with EGFR-mutant non-small cell lung cancer (NSCLC); however, evidence supporting its use in patients with diffuse brain metastases after multiple lines of therapy and very poor performance status remains limited. Here, we report the case of a 53-year-old man with EGFR L858R-mutant stage IV lung adenocarcinoma who developed multifocal progression involving the lungs, liver, bones, and brain after multiple prior treatments. At admission, he had diffuse brain metastases and an Eastern Cooperative Oncology Group (ECOG) performance status of 4, and he was unable to undergo whole-brain radiotherapy because of impaired consciousness. Dose-escalated furmonertinib was initiated and led to marked relief of neurological and respiratory symptoms within a few days. Subsequent imaging assessments showed sustained clinical benefit, with improvement in performance status and activities of daily living. This case suggests that, in EGFR-mutant advanced NSCLC with extensive CNS progression after multiline treatment failure in whom radiotherapy is not feasible, high-dose furmonertinib may represent a potential salvage option and may help inform individualized treatment strategies in this high-risk population. This single case is hypothesis-generating and larger cohorts/prospective studies are needed to confirm efficacy, safety, and appropriate patient selection.