A colon cancer diagnosis or a rectal cancer diagnosis typically involves a biopsy — studying suspicious tissue from the colon or rectum under a microscope. If doctors discover cancer they will run imaging tests to see how advanced the disease is and whether it has spread to other areas of the body. The tests you might encounter include:
Computed tomography (CT or CAT) scan In this test, cross-sectional images of the body created with X-rays are examined for signs that colorectal cancer has spread to other organs like the liver.Ultrasound This device can spot tumors by creating sound waves and transforming echoes into images on a screen.Magnetic resonance imaging (MRI) scan Radio waves and strong magnets produce detailed images that can help doctors see cancerous growths.Chest X-ray Doctors may use this test to see if cancer cells have spread to the lungs.Positron emission tomography (PET) scan Doctors inject a small amount of a radioactive sugar substance into the blood, then look to see how much it is absorbed by cells in different areas of the body. Cancer cells tend to absorb more of these sugars than normal cells because they require more energy to fuel their rapid growth. (1)
Staging Colon Cancer and Rectal Cancer
Each cancer has its own staging criteria. In the case of colon and rectal cancer, the system used is one that goes by the acronym TNM, which stands for tumor, node, and metastasis. The TNM system is organized around the answers to a series of questions.
Tumor (T) Has the tumor grown beyond the inside lining of the colon or rectum and into the wall? If so, how many layers deep is it?Node (N) Has the tumor spread to the lymph nodes? If so, where and how many? Metastasis (M) Has the cancer spread beyond the lymph nodes to other parts of the body? If so, where and how much?
Once doctors make all these assessments, they combine this information to stage the cancer. (2)
Colon and Rectal Cancer Stages
There are five stages of colon cancer, ranging from 0 to 4. Doctors may also follow the stage number with a letter that offers more information. Generally, the higher the number and letter, the more advanced the cancer. Stage 0 The cancer is in its earliest stage, called carcinoma in situ or intramucosal carcinoma. It has not grown beyond the inner layer (mucosa) of the colon or rectum (Tis, N0, M0). Stage 1 The cancer has grown into the submucosa, and possibly into the thick muscle layer beneath it (muscularis propria). It has not spread to nearby lymph nodes or distant sites (T1 or T2, N0, M0). Stage 2A The cancer has grown into the colon wall or rectum but not through it. It has not reached nearby organs or lymph nodes or spread to distant sites (T3, N0, M0). Stage 2B The cancer has grown through the wall of the colon or rectum but not into nearby tissue or organs. It has not spread to nearby lymph nodes or distant sites (T4a, N0, M0). Stage 2C The cancer has grown through the wall of the colon or rectum and is attached to or has grown into other nearby tissues or organs. It has not spread to nearby lymph nodes or distant sites (T4b, N0, M0). Stage 3A The cancer has grown into the submucosa and possibly the muscularis propria; it has spread to 1 to 3 nearby lymph nodes or into areas of fat near the lymph nodes, but not to distant sites (T1 or T2, N1/N1c, M0). — or — The cancer has grown into the submucosa and spread to 4 to 6 nearby lymph nodes but not to distant sites (T1, N2a, M0). Stage 3B The cancer has grown into the wall of the colon or rectum or through the visceral peritoneum (the inner lining of the abdominal cavity) but has not reached nearby organs. It has spread to 1 to 3 nearby lymph nodes or into areas of fat near the lymph nodes but not to distant sites (T3 or T4a, N1/N1c, M0). — or — The cancer has grown into the muscularis propria or into the wall of the colon or rectum and has spread to 4 to 6 nearby lymph nodes but not to distant sites (T2 or T3, N2a, M0). — or — The cancer has grown into the submucosa and possibly the muscularis propria. It has spread to 7 or more nearby lymph nodes but not to distant sites (T1 or T2, N2b, M0). Stage 3C The cancer has grown through the wall of the colon or rectum, including the tissues lining it (the visceral peritoneum), but has not reached nearby organs. It has spread to 4 to 6 nearby lymph nodes but not to distant sites (T4a, N2a, M0). — or — The cancer has grown into the wall of the colon or rectum, including the visceral peritoneum, but has not reached nearby organs. It has spread to 7 or more nearby lymph nodes but not to distant sites (T3 or T4a, N2b, M0). — or — The cancer has grown through the wall of the colon or rectum and is attached to or has grown into nearby tissues or organs. It has spread to at least one nearby lymph node or areas of fat close to it but not to distant sites (T4b, N1 or N2, M0). Stage 4A The cancer has spread to one distant organ, such as the liver or lungs, or distant set of lymph nodes, but not to distant parts of the lining of the abdominal cavity, the peritoneum (any T, any N, M1a). Stage 4B The cancer has spread to more than one distant organ or distant set of lymph nodes, but not to distant parts of the peritoneum (any T, any N, M1b). Stage 4C The cancer has spread to distant parts of the peritoneum (any T, any N, M1c). (3)
Colon & Rectal Cancer Survival Rates
The National Cancer Institute has collected data (most recently for the years 2004 through 2010) to create relative five-year survival rates for different kinds of cancer — the estimated percent of people at each stage who are expected to be alive five years after diagnosis. For colorectal cancers, available statistics are based on a previous version of the TNM cancer staging system that differs from the one used today; it does not have a stage 2C, for instance. Generally speaking, the higher the cancer’s stage, the poorer the prognosis. The fact that stage 3A colon cancer has a higher survival rate than stage 2A and 2B cancers seems odd, but it may reflect more aggressive treatment, among other factors, because patients with stage 3 colon cancer always get chemotherapy, while chemo’s ability to improve survival in stage 2 disease is controversial and related to microscopic examination of the tumor. Keep in mind that each cancer case is unique, and many factors apart from stage influence the outcome, such as a person’s age, overall health, and responsiveness to cancer treatment.
Stage 1: colon cancer, 92 percent; rectal cancer, 88 percentStage 2A: colon cancer, 87 percent; rectal cancer, 81 percentStage 2B: colon cancer, 65 percent; rectal cancer, 50 percentStage 3A: colon cancer, 90 percent; rectal cancer, 83 percentStage 3B: colon cancer and rectal cancer, 72 percentStage 3C: colon cancer, 53 percent; rectal cancer, 58 percentStage 4: colon cancer, 12 percent; rectal, 13 percent (4)
