Most colorectal cancer starts in the cells that line the inside of the colon or the rectum. The colon and rectum are part of your digestive system, where food is changed into energy and the body rids itself of waste matter. The human colon is a muscular, tube-shaped organ measuring about 4 feet long.

Causes

The exact cause of colorectal cancer is unknown, but several factors are thought to play a role. However, about 90 percent of people with the disease are older than 50. Sometimes, cells mutate and begin to grow and divide more quickly than normal cells. Rather than dying, these abnormal cells clump together to form tumors. If these tumors are cancerous, they can invade and kill your body's healthy tissues. From these tumors, cancer cells can metastasize (spread) and form new tumors in other parts of the body.

Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. More than one in 10 fatal colon cancers may be caused by smoking. Age is the number one risk factor for colon cancer. While wine has shown a protective effect, other alcohol appears to cause colon cancer. Results of one single study suggest working a night shift at least 3 nights a month for at least 15 years may increase the risk of colorectal cancer in women.

Symptoms

The symptoms of bowel cancer are very similar to common complaints such as piles or irritable bowel syndrome. Blood in your stool may be a sign of cancer, but it can also indicate other conditions. Bright red blood you notice on bathroom tissue may come from hemorrhoids or minor tears (fissures) in your anus, for example.

When symptoms are present, some of the most common symptoms are:

* Rectal bleeding
* Changes in bowel habits.
* Stomach cramps or abdominal pain.
* Anemia
* Frequent gas pains
* Blood in the stool.
* Unexplained weight loss.

Treatment

If the diagnosis is cancer, the tumour will then be 'staged'. This process, used with many cancers now, involves assessing how far the tumour has grown and spread. It helps doctors to work out what treatment is most appropriate and can provide an estimate of the chances of it a cure.

In cases of rare, inherited syndromes such as familial adenomatous polyposis, or inflammatory bowel disease such as ulcerative colitis, you may need removal of your entire colon and rectum as a prophylactic measure.

Radiation therapy in colorectal cancer has been limited to treating cancer of the rectum. There is a decreased local recurrence of rectal cancer in patients receiving radiation either prior to or after surgery.