Colon cancer is cancer of the large intestine (colon), the lower part of your digestive system. Rectal cancer is cancer of the last several inches of the colon. Together, they are often referred to as colorectal cancers.

Most cases of colon cancer begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Over time some of these polyps become colon cancers.

Polyps may be small and produce few, if any, symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying polyps before they become colon cancer.

Symptoms

1)A change in your bowel habits, including diarrhea or constipation or a change in the consistency of your stool for more than a couple of weeks
2)Rectal bleeding or blood in your stool
3)Persistent abdominal discomfort, such as cramps, gas or pain
4)A feeling that your bowel does not empty completely
5)Weakness or fatigue
5)Unexplained weight loss

Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms appear, they will likely vary, depending on the cancers size and location in your large intestine.

When to see a doctor

If you notice any symptoms of colon cancer, such as blood in your stool or a persistent change in bowel habits, make an appointment with your doctor.

Talk to your doctor about when you should begin screening for colon cancer. Guidelines generally recommend colon cancer screenings begin at age 50. Your doctor may recommend more frequent or earlier screening if you have other risk factors, such as a family history of the disease.

Causes

It is not clear what causes colon cancer in most cases. Doctors know that colon cancer occurs when healthy cells in the colon become altered. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But sometimes this growth gets out of control -- cells continue dividing even when new cells are not needed. In the colon and rectum, this exaggerated growth may cause precancerous cells to form in the lining of your intestine. Over a long period of time -- spanning up to several years -- some of these areas of abnormal cells may become cancerous.

Precancerous growths in the colon

Colon cancer most often begins as clumps of precancerous cells (polyps) on the inside lining of the colon. Polyps can appear mushroom-shaped. Precancerous growths can also be flat or recessed into the wall of the colon (nonpolypoid lesions). Nonpolypoid lesions are more difficult to detect, but are less common. Removing polyps and nonpolypoid lesions before they become cancerous can prevent colon cancer.

Inherited gene mutations that increase the risk of colon cancer

Inherited gene mutations that increase the risk of colon cancer can be passed through families, but these inherited genes are linked to only a small percentage of colon cancers. Inherited gene mutations do not make cancer inevitable, but they can increase an individuals risk of cancer significantly. Inherited colon cancer syndromes include:

1)Familial adenomatous polyposis (FAP). FAP is a rare disorder that causes you to develop thousands of polyps in the lining of your colon and rectum. People with untreated FAP have a greatly increased risk of developing colon cancer before age 40.

2)Hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC, also called Lynch syndrome, increases the risk of colon cancer and other cancers. People with HNPCC tend to develop colon cancer before age 50.

Both FAP and HNPCC can be detected through genetic testing. If you are concerned about your familys history of colon cancer, talk to your doctor about whether your family history suggests you have a risk of these conditions.

Western Medicine Treatment

The type of treatment your doctor recommends will depend largely on the stage of your cancer. The three primary treatment options are: surgery, chemotherapy and radiation.

Surgery for early-stage colon cancer

If your cancer is small, localized in a polyp and in a very early stage, your doctor may be able to remove it completely during a colonoscopy. If the pathologist determines that the cancer in the polyp doe not involve the base -- where the polyp is attached to the bowel wall -- then there is a good chance that the cancer has been completely eliminated.

Some larger polyps may be removed using laparoscopic surgery. In this procedure, your surgeon performs the operation through several small incisions in your abdominal wall, inserting instruments with attached cameras that display your colon on a video monitor. He or she may also take samples from lymph nodes in the area where the cancer is located.

Surgery for invasive colon cancer

If your colon cancer has grown into or through your colon, your surgeon may recommend a colectomy to remove the part of your colon that contains the cancer, along with a margin of normal tissue on either side of the cancer. Nearby lymph nodes are usually also removed and tested for cancer.

Your surgeon is often able to reconnect the healthy portions of your colon or rectum. But when that is not possible, for instance if the cancer is at the outlet of your rectum, you may need to have a permanent or temporary colostomy. This involves creating an opening in the wall of your abdomen from a portion of the remaining bowel for the elimination of body waste into a special bag. Sometimes the colostomy is only temporary, allowing your colon or rectum time to heal after surgery. In some cases, however, the colostomy may be permanent.

Surgery for advanced cancer

If your cancer is very advanced or your overall health very poor, your surgeon may recommend an operation to relieve a blockage of your colon or other conditions in order to improve your symptoms. This type of surgery is referred to as palliative surgery. The goal of palliative surgery is not to cure your cancer, but to relieve signs and symptoms, such as bleeding and pain. In specific cases where the cancer has spread only to the liver and if your overall health is otherwise good, your doctor may recommend surgery to remove the cancerous lesion from your liver. Chemotherapy may be used before or after this type of surgery. This treatment may improve your prognosis.

Chemotherapy

Chemotherapy uses drugs to destroy cancer cells. Chemotherapy can be used to destroy cancer cells after surgery, to control tumor growth or to relieve symptoms of colon cancer. Your doctor may recommend chemotherapy if your cancer has spread beyond the wall of the colon or if your cancer has spread to the lymph nodes. In people with rectal cancer, chemotherapy is typically used along with radiation therapy.

Radiation therapy

Radiation therapy uses powerful energy sources, such as X-rays, to kill any cancer cells that might remain after surgery, to shrink large tumors before an operation so that they can be removed more easily, or to relieve symptoms of colon cancer and rectal cancer.

Radiation therapy is rarely used in early-stage colon cancer, but is a routine part of treating rectal cancer, especially if the cancer has penetrated through the wall of the rectum or traveled to nearby lymph nodes. Radiation therapy, usually combined with chemotherapy, may be used after surgery to reduce the risk that the cancer may recur in the area of the rectum where it began.

Targeted drug therapy

Drugs that target specific defects that allow cancer cells to proliferate are available to people with advanced colon cancer, including bevacizumab (Avastin), cetuximab (Erbitux) and panitumumab (Vectibix). Targeted drugs can be given along with chemotherapy or alone. Targeted drugs are typically reserved for people with advanced colon cancer.

Some people are helped by targeted drugs, while others are not. Researchers are working to determine who is most likely to benefit from targeted drugs. Until then, doctors carefully weigh the limited benefit of targeted drugs against the risk of side effects and the expensive cost when deciding whether to use these treatments.

Adopted from mayoclinic.com