Pulsatile High-dose Furmonertinib in EGFR-mutant NSCLC With Leptomeningeal Metastasis

The goal of this clinical trial is to clarify the efficacy and safety of the high-dose alternate-day furmonertinib in NSCLC with leptomeningeal metastasis. It will also explore the mechanism by which the high-dose alternate-day administration regimen enhances efficacy from a pharmacokinetic perspective, and investigate the impact of co-occurring mutations on the efficacy and prognosis of furmonertinib in the treatment of EGFR-mutant NSCLC with leptomeningeal metastasis. The main questions it aims to answer are: Does the high-dose alternate-day administration regimen have definite efficacy? Does the high-dose alternate-day administration regimen have favorable safety? Does the high-dose alternate-day administration regimen improve efficacy by increasing the cerebrospinal fluid (CSF) concentration and CSF penetration rate of the drug? Which co-occurring mutations may affect the efficacy and prognosis of patients with EGFR-mutant NSCLC and leptomeningeal metastasis? Participants will enter Cohort A (320mg qod po) or Cohort B (160mg qd po) to receive furmonertinib based on their own willingness and the clinician's decision, until disease, progression or uncontrollable adverse reactions occur. All patients in Cohort A will undergo efficacy and safety evaluation, with some also participating in pharmacokinetic study; patients in Cohort B will only undergo pharmacokinetic study. Efficacy and safety evaluation will be conducted through imaging examinations, neurological function assessment scales, quality of life self-assessment scales, and adverse event records. Pharmacokinetic study will be carried out by detecting the plasma concentrations and CSF concentrations of furmonertinib and its active metabolites, and calculating the CSF penetration rate for evaluation.