What is colorectal cancer?Colorectal cancer is cancer of the colon or rectum. Colorectal cancer includes cancerous growths in the colon, rectum, anus, and appendix. Most types of colorectal cancer begin with polyps (grape-shaped growths on the lining of the colon and rectum). Polyps are very common in people older than 50 years of age and usually are benign (not cancerous). But some
polyps can slowly develop over the years into cancer.
The colon (known as the large bowel or large intestine) joins the small intestine to the rectum. Each part of the digestive system plays a different role in processing food. Completely digested food moves from the small intestine into the colon where water is removed so that the remaining waste (feces) is firm as it leaves the body. The rectum is the last part of the colon. Waste is stored in the rectum until it leaves the body through the anus in a bowel movement.
Most colon and rectal cancers originate from benign wart-like growths on the inner lining of the colon or rectum called polyps. Not all polyps have the potential to transform into cancer. Those that do have the potential are called adenomas. It takes more than 10 years in most cases for an adenoma to develop into cancer. This is why some colon cancer prevention tests are effective even if done at 10-year intervals. This 10-year interval is too long, in some cases, such as in persons with ulcerative colitis or Crohn's colitis, and in persons with a strong family history of colorectal cancer or adenomas.
Over 95% of colon and rectal cancers are adenocarcinomas. These are cancers of the cells that line the inside of the colon and rectum. There are some other, more rare, types of tumors of the colon and rectum, but the facts given here refer only to adenocarcinomas. Colon and rectal cancer have many features in common and are often referred to together as colorectal cancer. They are discussed together here except for the section about treatment. At that point they will be discussed separately. Cancer of the small intestine is very rare, so when people talk about bowel cancer, they usually mean colorectal cancer. Colorectal cancer is the third most common cancer for both men and women in Canada.
More information on colorectal cancerWhat is colorectal cancer? - Colorectal cancer is cancer of the colon or rectum. Colorectal cancer includes cancerous growths in the colon, rectum, anus, and appendix.
What causes colorectal cancer? - Colorectal cancer is a disease resulting from mutations in epithelial cells lining the gastrointestinal tract.
What're the risk factors for colorectal cancer? - Risk factors for colorectal cancer include family history of colon cancer, age, smoking, diet, virus.
What're the symptoms of colorectal cancer? - Symptoms of colorectal cancer vary depending on the location of the cancer within the colon or rectum, though there may be no symptoms at all.
How is colorectal cancer screened and diagnosed? - Colorectal cancer usually is diagnosed by a sigmoidoscopy or colonoscopy. Screening for colorectal cancer is recommended in individuals who are at increased risk.
What's treatment for colorectal cancer? - Treatment for colorectal cancer depends mostly on the size, location and extent of the tumor. Surgery to remove the tumor is the most common treatment.
How to prevent the development of colorectal cancer? - Colorectal cancer can be associated with known risk factors. Many risk factors are modifiable though not all can be avoided.
What is a colon polyp? - Colon polyps are growths that stick out from the lining of the lower intestine. Polyps can develop anywhere in your large intestine.
What're the symptoms of colon polyps? - Smptoms of colon polyps include rectal bleeding, blood in stool, constipation or diarrhea, pain or obstruction.
What's the treatment for colon polyps? - For people with familial colon polyps, complete removal of the large intestine and rectum eliminates the risk of cancer.