Following diagnosis, oncologists and pathologists must analyze the extent to which the cancer has progressed and determine whether it has metastasized to other organs. This process, called "staging," is crucial in guiding treatment.
Cancer confined to the mucosa of the colon wall is classified as stage I and is easily removable by surgery in the great majority of cases. When the cancer has penetrated deeper into the muscle layers of the colon, or has just perforated the colon wall, it is classified as stage II. Stage II colon cancer also carries a fairly good prognosis. Stage III is defined by detection of cancer in nearby lymph nodes, tissues or organs. Stage IV colorectal cancer defines metastasis to one or more distant organs, such as the lungs.
The outlook diminishes as stages advance; surgery is usually no longer a curative option for cancer not contained within the colon or isolated to nearby tissue (colon cancer with isolated liver or lung metastasis can rarely be treated effectively with surgery). Five-year survival rates for stage I colon cancer are very good, at about 90%, while the median survival plummets to just six months in advanced stage IV cancer.65
A valuable innovation in cancer prognostic technology is circulating tumor cell testing. Circulating Tumor Cell testing involves the detection of cancer cells in the bloodstream. These circulating tumor cells are the "seeds" that break away from the primary site of cancer and spread to other parts of the body. Understanding circulating tumor cells is critically important since it is the spread of cancer to other parts of the body—and not the primary cancer—that is very often responsible for the death of a person with cancer. For a detailed discussion of circulating tumor cell testing, please refer to section three of the “Cancer Treatment: The Critical Factors” protocol.