Patients with responding disease after receiving at least 6 courses of chemotherapy may undergo surgery. Beginning within 10 weeks after surgery, patients receive simplified LV5FU2 chemotherapy comprising leucovorin calcium IV over 2 hours on day 1, fluorouracil IV over 46 hours beginning on day 1, and oral celecoxib twice daily beginning on day 1. Treatment repeats every 14 days for at least 12 courses.