Intrathecal Pemetrexed for Leptomeningeal Metastasis

This is a phase I/II clinical trial. The objective of the study is patients with leptomeningeal metastases from solid tumors. Pemetrexed (Alimta, Eli Lilly and Company) is administrated by intrathecal injection, plus dexamethasone 5 mg, twice per week for 2 weeks, followed by once per week for 4 weeks. In phase I study, the initial dose of intrathecal pemetrexed is 15 mg, escalated to 20 mg, and then 25 mg.... A minimum of three patients and a maximum of six are enrolled in each cohort. A dose-limiting toxicity is defined as grade 3 neurological toxicities (e.g., chemical meningitis) or other grade 4 toxicity. If none of the three patients experiences any dose-limiting toxicity, the subsequent three patients are enrolled at the next higher dosage level. If one of three patients experiences a dose-limiting toxicity, up to three more patients are enrolled at the same level. The maximum-tolerated dose is defined as the dose where 0/3 or 1/6 patients experiences a dose-limiting toxicity with at least two patients encountering dose-limiting toxicity at the higher dose. If more than two patients experience a dose-limiting toxicity, that level is considered too toxic. The maximum-tolerated dose is exceeded and an additional three patients should be treated at the next lower dose level. Folic acid 200-400 μg is administered orally once daily, prior to the first intrathecal pemetrexed, until 21 days after the last intrathecal pemetrexed. A single dose of vitamin B12 1000 μg is administered by intramuscular injection before the first intrathecal pemetrexed, once per 3 weeks. In phase II study, the maximum-tolerated dose determined in phase I study is chosen.