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Abstract Purpose: The treatment of leptomeningeal metastasis (LM), a serious complication of advanced non-small cell lung cancer (NSCLC), presents challenges, particularly in patients with EGFR exon 20 insertion (ex20ins) mutations. Methods: This study retrospectively analyzed data from 10 EGFR ex20ins-mutated NSCLC patients with LM admitted at our institution from May 2011 to June 2023. Circulating tumor DNA (ctDNA) from cerebrospinal fluid (CSF) and matched plasma samples was analyzed using next-generation sequencing. All patients received high-dose furmonertinib combined with intraventricular chemotherapy (IVC) as salvage therapy. Data on patient demographics, treatment efficacy, and safety outcomes were collected. Results: The most common insertion mutation identified in this study was p. A767V769dup (n = 4, 40%), followed by D770-N771insY (n = 2, 20%). Nine patients had EGFR ex20ins occurring in the EGFR loop region following the C-helix, whereas only one patient had an EGFR ex20ins (A763Y764insFQEA) occurring in the C-helix of the tyrosine kinase domain. LM response assessment using the RANO-LM criteria revealed that 6 patients (60%, 95% CI 26. 2–87. 8%) achieved a response, 3 had stable disease, and 1 had progressive disease. The median progression-free survival and overall survival were estimated to be 6. 5 months and 8. 8 months, respectively. The most commonly reported treatment-related adverse events were rash (n = 7) and diarrhea (n = 7), with no treatment-related deaths occurring. Conclusions: The current study demonstrated that high-dose furmonertinib plus IVC as salvage treatment for patients with LM harboring EGFR ex20ins mutations had promising clinical benefits and a manageable safety profile.
Yu et al. (Mon,) studied this question.