Colon cancer, also called colorectal cancer, is the uncontrolled growth of cancer cells in the lining of the colon, the part of the large intestine between the caecum and the rectum. Cancer of the colon is the third most common cancer in both men and women. The outcome, or prognosis, of colon cancer depends on the stage, or advancement of the cancer. Stage 4 colon cancer is the most advanced stage and has the worst prognosis.
Colon cancer is divided into four stages based on the size, location and characteristics of the tumours. Stage 1 is the least severe stage and has the best prognosis while stage 4 is the most severe. Although the cancer may or may not have grown through the wall of the colon and may or may not involve the lymph nodes, all stage 4 colon cancers are marked by the tumours spread (or metastasis) to other organs such as the liver, lungs, abdominal cavity or ovaries.
Patients in the early stages of colon cancer are not likely to exhibit symptoms. This is why early detection techniques like colonoscopy are important as those who find their cancer while in the early stages have a positive prognosis. However, by stage 4, patients are likely experiencing symptoms including a change in bowel habits (either constipation or diarrhoea), bloody stool, abdominal discomfort, weakness, fatigue or unexplained weight loss.
Surgery to remove the tumours is the primary treatment for all stages of colon cancer except for stage 4. Since stage 4 means that the tumours have spread to other organs surgery may still be performed but not usually as a cure. For patients with stage 4 cancer the surgery is likely performed to relieve or prevent blockage of the colon. However, the prognosis is dependent on the extent and number of the metastases present. If there are five or less tumours on an organ such as the liver, they may be able to be removed in the surgery adding years to your life, or even curing the cancer.
Because surgery is unlikely to remove all the tumours that have spread to other organs, chemotherapy is administered to patients in stage 4. Chemotherapy can be given intravenously; however, patients who have metastasised tumours on the liver will respond better to chemotherapy administered through an artery that leads to the liver. The disadvantage to this method is that tumours anywhere else in the body will continue to grow. The prognosis for those patients with only a few metastasised tumours in the liver however is good as the arterial chemotherapy can prolong life or even provide a cure.
For patients with cancer, doctors provide a prognosis in terms of survival rate. The survival rate is the percentage of patients who live at least five years after diagnosis. Because a patient's prognosis is dependent on not only the stage of the cancer but also their overall health, these survival rates should only be used as a general guide. The survival rate for stage 4 colon cancer is 8 per cent, meaning only 8 per cent of patients will live five years after diagnosis.