S9915 Triacetyluridine, Fluorouracil, and Leucovorin in Treating Patients With Unresectable, Locally Advanced, or Metastatic Cancer of the Esophagus or Stomach

DISEASE CHARACTERISTICS: * Histologically or cytologically proven unresectable, locally advanced or metastatic adenocarcinoma of the stomach or gastroesophageal junction * No known brain metastases * Negative brain imaging required for neurologic signs and symptoms PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Zubrod 0-1 Life expectancy: * Not specified Hematopoietic: * Absolute neutrophil count at least 1,500/mm\^3 * Platelet count greater than 100,000/mm\^3 Hepatic: * Bilirubin no greater than upper limit of normal (ULN) * SGOT or SGPT no greater than 1.5 times ULN (5 times ULN if liver tumor present) Renal: * Creatinine no greater than ULN Other: * Not pregnant or nursing * Fertile patients must use effective contraception * Must be able to swallow oral medication * No AIDS syndrome or HIV-associated complex * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or adequately treated stage I or II cancer in complete remission PRIOR CONCURRENT THERAPY: Biologic therapy: * No prior biologic therapy * No concurrent biologic therapy Chemotherapy: * No prior chemotherapy for advanced or metastatic gastric cancer * At least 6 months since prior chemotherapy as adjuvant or radiation sensitizer Endocrine therapy: * Not specified Radiotherapy: * At least 1 month since prior radiotherapy and recovered * No concurrent radiotherapy Surgery: * At least 3 weeks since prior major surgical resection of intra-abdominal organs and recovered