OUTLINE: Patients receive trimetrexate glucuronate (TMTX) IV over 1 hour on day 1. Beginning 18 hours after the TMTX dosage, patients receive leucovorin calcium (CF) IV over 2 hours. Immediately after the completion of the CF infusion, patients receive an IV bolus injection of fluorouracil (5-FU). Beginning 4 hours after the 5-FU infusion, patients receive oral CF every 6 hours for 6 doses. Treatment repeats every 14 days in the absence of disease progression or unacceptable toxicity or as long as the disease remains inoperable. Patients are followed every 3 months for 1 year, every 6 months for 3 years, and then annually thereafter.