5-Fluorouracil Followed by Interferon-alfa-2b in Previously-treated Metastatic Gastrointestinal, Kidney, or Lung Cancer

Inclusion Criteria: * Patients must have histologically-proven, metastatic gastrointestinal, kidney, or lung cancer who have had disease progression on at least two prior systemic therapies. * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 and estimated survival of at least 3 months. * Patients must be felt to have recovered from effects of prior therapy, such as past expected white blood count nadir for chemotherapy (\> 2 weeks for most agents, \> 6 weeks for nitrosoureas or mitomycin-C) * Patient consent must be obtained prior to entrance onto study. * White blood count \> 3500/mm3; platelet count of at least 100,000/mm3; hemoglobin \> 9.0 gm/dl; bilirubin, Aspartate aminotransferase (AST), Alanine aminotransferase (ALT) less than 3 times the upper limit of normal; serum creatinine \< 1.8. * Corticosteroids and immunosuppressive agents are not permitted during the course of the study. Patients must have received no corticosteroids or immunosuppressive medications at least 2 weeks prior to entrance on-study. * Patients with elevated temperatures \> 100.5 degrees F, must have sources of occult infection excluded. * Women of childbearing potential must have a negative pregnancy test and must take adequate precautions to prevent pregnancy during treatment. Exclusion Criteria: * Evidence of significant cardiovascular disease including history of recent (\< 6 months) myocardial infarction, uncompensated congestive heart failure, primary cardiac arrhythmias (not due to electrolyte disorder or drug toxicity, for example) beyond occasional PVC's, angina, or cerebrovascular accident. * Prior history of psychiatric disorder that could be exacerbated by interferon therapy or which could preclude completion of this therapy. * Pregnancy or lactation. * History of hypersensitivity to interferon alfa or fluoropyrimidines. * History of severe debilitating pulmonary disease, such as chronic obstructive pulmonary disease requiring continuous oxygen therapy. * History of autoimmune disease requiring immunosuppression. * Documented inflammatory joint or systemic inflammatory disease (such as Lupus) which could be exacerbated by interferon therapy.