General Information About Colon Cancer

• Colon cancer is a disease in which malignant (cancer) cells form in the tissues of the colon.
• The colon is part of the body’s digestive system.
• The digestive system is made up of the esophagus, stomach, and the small and large intestines.
• The colon (large bowel) is the main part of the large intestine and is about 5 feet long. Together, the rectum and anal canal make up the last part of the large intestine and are about 6-8 inches long.
• Colon cancer is a disease in which malignant (cancer) cells form in the tissues of the colon.
• Health history affects the risk of developing colon cancer.
• Signs of colon cancer include blood in the stool or a change in bowel habits.

Risks of developing colon cancer

Risk factors for colorectal cancer include the following:

• Having a family history of colon or rectal cancer in a first-degree relative (parent, sibling, or child).
• Having a personal history of cancer of the colon, rectum, or ovary.
• Having a personal history of high-risk adenomas (colorectal polyps that are 1 centimeter or larger in size or that have cells that look abnormal under a microscope).
• Having inherited changes in certain genes that increase the risk of familial adenomatous polyposis (FAP) or Lynch syndrome (hereditary nonpolyposis colorectal cancer).
• Having a personal history of chronic ulcerative colitis or Crohn disease for 8 years or more.
• Having three or more alcoholic drinks per day.
• Smoking cigarettes.
• Being African-American.
• Being obese.
• Older age is a main risk factor for most cancers. The chance of getting cancer increases as you get older.

Tests that examine the colon and rectum are used to diagnose colon cancer

Physical exam and health history

Digital rectal exam: An exam of the rectum. The doctor or nurse inserts a lubricated, gloved finger into the rectum to feel for lumps or anything else that seems unusual.

Fecal occult blood test (FOBT): A test to check stool) for blood that can only be seen with a microscope. A small sample of stool is placed on a special card or in a special container and returned to laboratory. Blood in the stool may be a sign of polyps, cancer, or other conditions. There are two types of FOBTs:

• Guaiac FOBT: The sample of stool on the special card is tested with a chemical. If there is blood in the stool, the special card changes color.
• Immunochemical FOBT: A liquid is added to the stool sample. This mixture is injected into a machine that contains antibodies that can detect blood in the stool. If there is blood in the stool, a line appears in a window in the machine. This test is also called fecal immunochemical test or FIT.

Reverse transcription–polymerase chain reaction (RT–PCR) test: A laboratory test in which the amount of a genetic substance called mRNA made by a specific gene is measured. An enzyme is used to convert a specific piece of RNA into a matching piece of DNA, which can be amplified (made in large numbers) by another enzyme called DNA polymerase. The amplified DNA copies help tell whether a specific mRNA is being made by a gene. RT–PCR can be used to check the activation of certain genes that may indicate the presence of cancer cells.

Sigmoidoscopy: A procedure to look inside the rectum and sigmoid (lower) colon for polyps (small areas of bulging tissue), other abnormal areas, or cancer. A sigmoidoscope is inserted through the rectum into the sigmoid colon. A sigmoidoscope is a thin, tube-like instrument with a light and a lens for viewing.

Colonoscopy: A procedure to look inside the rectum and. A colonoscope is inserted through the rectum into the colon. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.

Virtual colonoscopy: A procedure that uses a series of x-rays called computed tomography to make a series of pictures of the colon.

Prognosis (chance of recovery) of colon cancer

The prognosis and treatment options depend on the following:

• The stage of the cancer (whether the cancer is in the inner lining of the colon only or has spread through the colon wall, or has spread to lymph nodes or other places in the body).
• Whether the cancer has blocked or made a hole in the colon.
• Whether there are any cancer cells left after surgery.
• Whether the cancer has recurred.
• The patient’s general health.
• The prognosis also depends on the blood levels of carcinoembryonic antigen (CEA) before treatment begins. CEA is a substance in the blood that may be increased when cancer is present.

Cancer may spread from where it began to other parts of the body.

• When cancer spreads to another part of the body, it is called metastasis.
• Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.
• The metastatic tumor is the same type of cancer as the primary tumor. For example, if colon cancer spreads to the lung, the cancer cells in the lung are actually colon cancer cells. The disease is metastatic colon cancer, not lung cancer.

Stages of colon cancer:

Stage 0 (Carcinoma in Situ): In stage 0, abnormal cells are found in the mucosa (innermost layer) of the colon wall. These abnormal cells may become cancer and spread into nearby normal tissue

Stage I: In stage I colon cancer, cancer has formed in the mucosa (innermost layer) of the colon wall and has spread to the submucosa (layer of tissue next to the mucosa) or to the muscle layer of the colon wall.

Stage II: Cancer has spread through the muscle layer of the colon wall to the serosa outermost layers of the colon wall or nearby organs.

Stage III: Cancer has spread to surrounding lymph glands.

Stage IV: Cancer has spread through the blood and lymph nodes to other parts of the body, such as the lung, liver, abdominal wall, or ovary.