The purpose of this study is to determine whether the combination of a 5-Fluorouracil (5-FU) and interferon, which is able to stimulate the immune system to kill cancer cells, will help to increase tumor shrinkage in previously-treated metastatic gastrointestinal, kidney, or lung Cancer.

Interferon with continuous infusion 5-Fluorouracil (5-FU) regimens have shown response rates ranging from 0-43% in various cancers. Monthly bolus 5-FU + interferon-alfa-2b has not undergone formal phase II testing. In a small pilot study, a 5 consecutive day schedule of 5-FU and interferon-alfa-2b resulted in the limiting toxicities of diarrhea and mucositis. A more limited schedule was recommended. Therefore, it is reasonable to examine such a schedule. In the current study, 5-FU will be followed by interferon-alfa-2b daily for 3 days to attempt to benefit from both the biochemical and immunologic mechanisms described above.

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.