Like all cancers, colorectal cancer occurs when cells grow out of control. The cancer cells form a tumor, which invades and destroys nearby tissue. The cells also can break off and move to other parts of the body, where they can start a new tumor.
Colorectal cancer occurs in the lower intestine, which includes the colon and rectum. The colon, a 5- to 6-foot-long muscular tube, is the final part of the intestinal tract that ends in the rectum. The rectum comprises the intestinal tract's final few inches.
Anyone can get the disease. Men and women are equally susceptible. Chances of developing colorectal cancer increase with age; the disease is more common after age 50. Among ethnic groups in the United States, African-Americans have the highest incidence and highest rate of death from colorectal cancer.
Who is at greatest risk? Individuals with personal or family history of colorectal cancer or with chronic inflammatory bowel disease (Crohn's disease or ulcerative colitis).
Currently, no sure-fire method exists for preventing colorectal cancer. This makes early detection by having a screening test extremely important, especially if you're over age 50.
Colorectal cancer is thought to develop slowly over several years. Almost all colorectal cancers begin as a small growth or polyp, also known as an adenoma.
A polyp is a growth of tissue that erupts from the lining of the large intestine. A small number of polyps will grow into cancer; most won't. One statistic says that less than 1 percent of all polyps ever become cancerous. The larger the polyp, the greater the chance it contains cancerous cells. To prevent cancer, your doctor will remove polyps during screening.
Researchers don't know the exact cause of colorectal cancer. However, scientists have been able to identify factors that increase your chance of getting the disease. These risk factors include:
Unfortunately, the early stages of the disease, when it's most curable, usually don't produce any symptoms. By the time symptoms show up, the cancer may be far advanced. Still, you should watch for the following: a marked change in bowel habits, rectal bleeding, marked thinning of the stools, and unexplained weight loss.