Patients receive pemetrexed disodium IV over 10 minutes and carboplatin IV over 30 minutes on day 1. Treatment repeats every 21 days for up to 6 courses in the absence of disease progression or unacceptable toxicity. Patients who develop progressive disease in the CNS only may receive whole-brain radiotherapy and then continue chemotherapy after completion of whole-brain radiotherapy for up to 6 courses.