Intrathecal Pemetrexed for Leptomeningeal Metastasis From Lung Adenocarcinoma That Progressed After Osimertinib.

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.