 Patients receive pemetrexed disodium IV over 10 minutes on day 1 and gemcitabine IV over 30 minutes on days 1 and 8. Patients also receive cyanocobalamin intramuscularly once every 9 weeks and folic acid orally once daily beginning on day -6 and continuing until 3 weeks after the completion of study therapy. Treatment repeats every 3 weeks for up to 6 courses in the absence of disease progression or unacceptable toxicity. 