 There are two common combinations of chemotherapy drugs used to treat cancer of the colon, rectum, or appendix that has spread to the abdomen. One uses 5-fluorouracil also called 5-FU, leucovorin and oxaliplatin, and is called FOLFOX. The other uses 5-FU, leucovorin, and irinotecan, and is called FOLFIRI. The Food and Drug Administration FDA has approved each of these combinations as treatment for colon or rectal cancer. Each is given through the veins. 