Intra-pemetrexed Plus Third-generation Small Molecule TKI Drugs (e.g. 'Osimertinib') Versus Third-generation Small Molecule TKI Drugs Alone for Leptomeningeal Metastasis From Epidermal Growth Factor Receptor Mutation-Positive Non-Small-cell Lung Cancer

Double-dose of TKI (e.g. 'osimertinib' 160 mg) was administered orally once daily until disease progression or unmanageable drug-related toxicity.

Pemetrexed 15 mg was administered with dexamethasone 5 mg via intraventricular or via lumbar puncture. First, induction intrathecal chemotherapy, twice per week for 2 weeks; then consolidation intrathecal chemotherapy, once per week for 4 weeks; and maintenance intrathecal chemotherapy, once per month until disease progression or unmanageable drug-related toxicity.