In certain instances of colon cancer metastasis and recurrence, surgery is either contraindicated or would not be curative. This can occur when the patient's condition is such that the risk of surgery outweighs the presence of cancer, or when the cancer is so advanced that there is no cure. Since the goal of chemotherapy under these circumstances is to slow down the growth of the cancer and to improve the patient's quality of life, it is called palliative chemotherapy

Chemotherapy uses cytotoxic drugs - drugs that are toxic to cells - to attack cancer cells. The drugs used in chemotherapy are designed to attack fast growing cells, such as those of colon cancer. Because of this, patients often experience side effects that can include nausea (and vomiting), mouth sores, the thinning or loss of hair, diarrhea, and the shedding of skin in the hands and feet.

The most prevalent drug used for the treatment of colon cancer is Fluorouracil (5-FU). This drug incorporates itself in a cell's normal DNA and, by masquerading as a normal building block, prevents malignant cells from dividing. 5-FU is normally given in conjunction with a second drug to increase effectiveness. The second drug is usually either Levamisole, which is an immunity-stimulating agent, or Leucovorin (folic acid), which binds to the enzymes and makes 5-FU more toxic to cancer cells.

Chemotherapy can be administered intravenously, intramuscularly, orally, or subcutaneously (under the skin). Sometimes, your oncologist and surgeon, may recommend that a portocath, or peripherally inserted central catheter (PIC), be implanted in your body so that the drugs can be administered easily through to catheter, delivering the chemotherapy directly to the bloodstream.

In cases involving widespread metastasis to the liver, chemotherapy can also be administered directly to the hepatic artery. The technique is called perfusion because it forces large dosages of the chemotherapy drugs directly to the organ through the hepatic artery, the main blood supply from the heart.

Sometimes, patients who are not candidates for surgery ask why they shold undergo chemotherapy if it cannot cure their cancer. Why go through a year of nausea, hair loss, mouth sores, and other side-effects? The decision to undergo chemotherapy in cases where the cancer is thought to not be curable is a difficult personal decision. Yet, with chemotherapy, it may be possible to increase the patient's survival time, and to enhance his or her well-being. This can add to the patient's quality of life in a way that outweighs the side-effects of the chemotherapy.