Combination Chemotherapy Plus Interferon Alfa Followed by Filgrastim in Treating Patients With Gastrointestinal Tract Cancer

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Interferon alfa may interfere with the growth of cancer cells. Colony-stimulating factors such as filgrastim may increase the number of immune cells found in bone marrow or peripheral blood and may help a person recover from the side effects of chemotherapy. Combining chemotherapy with interferon alfa may kill more tumor cells. PURPOSE: Phase II trial to study the effectiveness of combining chemotherapy and interferon alfa followed by filgrastim in treating patients who have gastrointestinal tract cancer.