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

Inclusion Criteria: 1. Patients with non-small cell lung cancer (NSCLC) confirmed by histopathological or cytopathological examination 2. Patients with EGFR exon 19 deletion or exon 21 L858R mutation 3. Patients with leptomeningeal metastasis (LMD) confirmed by positive cerebrospinal fluid (CSF) cytology (within 28 days prior to the first dose administration) and with at least 1 LMD lesion that can be repeatedly evaluated by magnetic resonance imaging (MRI) 4. Patients with disease progression after first-line tyrosine kinase inhibitor (TKI) treatment 5. Aged ≥18 years and ≤85 years, with no gender restrictions. 6. Sufficient organ function, defined as: absolute neutrophil count ≥ 1.5×10⁹/L, platelet count ≥ 75×10⁹/L, hemoglobin ≥ 90g/L total bilirubin ≤ 1.5×upper limit of normal (ULN) alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5×ULN (for patients with liver metastasis, total bilirubin can be relaxed to ≤ 3×ULN, and ALT/AST can be relaxed to ≤ 5×ULN) serum creatinine ≤ 1.5×ULN or creatinine clearance ≥ 50 mL/min (calculated by the Cockcroft-Gault formula) 7. For patients enrolled in the pharmacokinetic study: no prior treatment with furmonertinib (either in combination or as monotherapy) 8. Patients who have signed the informed consent form, are willing to receive treatment under this protocol, can adhere to medication administration, and have good compliance. Exclusion Criteria: 1. Unable to complete the baseline assessment form 2. Complicated with severe or uncontrolled systemic diseases, including active infection, electrolyte disturbance, bleeding tendency, etc. 3. Pregnant or lactating women, or those with planned pregnancy during the study or within 6 months after the study ends 4. Presence of central nervous system complications requiring emergency neurosurgical intervention 5. Suffering from other malignant tumors or having a history of other malignant tumors 6. Complicated with severe brain diseases or mental illnesses that affect the patient's ability to report symptoms by themselves 7. Individuals without legal capacity, or those for whom medical or ethical reasons affect the continuation of the study 8. Other circumstances deemed unsuitable for participation in this study by the researcher. 9. Patients with a severe allergic diathesis, especially those who have experienced severe drug allergies or other serious adverse reactions during previous treatment with tyrosine kinase inhibitors (TKIs).