Colorectal cancer is a disease in which abnormal cells in the colon or rectum divide uncontrollably, ultimately forming a malignant tumor. (The colon and rectum are parts of the body’s digestive system, which takes up nutrients from food and water and stores solid waste until it passes out of the body.)
Most colorectal cancers begin as a polyp, a growth in the tissue that lines the inner surface of the colon or rectum. Polyps may be flat, or they may be raised. Raised polyps may grow on the inner surface of the colon or rectum like mushrooms without a stalk (sessile polyps), or they may grow like a mushroom with a stalk (pedunculated polyps). Polyps are common in people older than 50 years of age, and most are not cancers. However, a certain type of polyp known as an adenoma may have a higher risk of becoming a cancer.
Colorectal cancer is the third most common type of non-skin cancer in both men (after prostate cancer and lung cancer) and women (after breast cancer and lung cancer). It is the second leading cause of cancer death in the United States after lung cancer. The rates of new colorectal cancer cases and deaths among adults aged 50 years or older are decreasing in this country. However, the incidence is increasing among younger adults. It is estimated that a total of 136,830 people in the United States will be diagnosed with colorectal cancer and 50,310 people will die from it in 2014
Although the major risk factors for colorectal cancer are a family history and older age, several other factors have been associated with increased risk, including excessive alcohol use, obesity, being physically inactive, cigarette smoking, and, possibly, diet.
In addition, people with a history of inflammatory bowel disease (such as ulcerative colitis or Crohn disease) have a higher risk of colorectal cancer than people without such conditions. And people who have a family history of colorectal cancer or certain inherited conditions (such as Lynch syndrome and familial adenomatous polyposis) also have an increased risk of colorectal cancer.
Several screening tests have been developed to help doctors find colorectal cancer early, when it may be more treatable. Some tests that detect adenomas and polyps can actually prevent the development of cancer because these tests allow growths that might otherwise become cancer to be detected and removed. That is, colorectal cancer screening may be a form of cancer prevention, not just early detection.
Expert medical groups strongly recommend screening for colorectal cancer. Although minor details of the recommendations may vary, these groups generally recommend that people at average risk of colorectal cancer get screened at regular intervals with high-sensitivity fecal occult blood tests (FOBT), sigmoidoscopy, or colonoscopy beginning at age 50. People at increased risk because of a family history of colorectal cancer or polyps or because they have inflammatory bowel disease or certain inherited conditions may be advised to start screening before age 50 and/or have more frequent screening.
Both polyps and colorectal cancers can bleed, and FOBT checks for tiny amounts of blood in feces (stool) that cannot be seen. (Blood in stool may also indicate the presence of conditions that are not cancer, such as hemorrhoids.)
Stool test looking for occult blood is necessary to perform in healthy people over 50 years old every couple years. The yearly blood cells count may discover iron defficency or even an anemia as sign of an colorectal cancer, but only stool test is valid for the earliest diagnose of this condition.