- All patients will receive four chemotherapy drugs: 5-Fluorouracil, leucovorin, oxaliplatin, and irinotecan. The drugs are given intravenously over 2 days every 2 weeks (one cycle) for 12 cycles (about 6 months), either at the National Institutes of Health (NIH) Clinical Center or at home with a referring oncologist. Patients in the surgery group who have tumors in the peritoneum will receive an additional set of chemotherapy drugs in a separate treatment.