Diagnosing colorectal cancer

Do you know what the risk factors and warning signs are for colorectal cancer (cancer of the lower bowel)? Here's some important information on risk factors – and on tests that can help screen for colorectal cancer.

Risk factors

  • Age: As you age, your risk for colorectal cancer increases. In fact, more than 90% of those afflicted with the condition are over the age of 50. This is partly due to the fact that colorectal cancer develops over a period of at least 10 years.
  • Diet: A number of studies show that what you eat may be linked to your likelihood of developing colorectal cancer. For instance, diets rich in fibre and whole-grains are associated with a reduced risk. Conversely, diets high in alcohol, processed meats, or red meats may elevate your risk. Cooking meats at high temperatures can create chemicals called heterocyclic amines (HCAs) that may increase your risk of developing cancer.
  • Lifestyle: Certain lifestyle habits like smoking or consuming 2 or more alcoholic drinks per day also increases your risk of developing colorectal cancer. Physical inactivity and obesity can further contribute to this.
  • Family history: As with many other forms of cancer, the odds of getting colorectal cancer go up if a family member, particularly a parent or sibling, has had the disease. While this may be in part to genetic factors, it may also result from living in a similar environment or adopting a similar lifestyle. People with a family history of inherited breast cancer, uterine, or ovarian cancer are also at an increased risk for developing colorectal cancer.
  • Polyps: Polyps are growths of tissue that can be found in the colon. These growths can be benign (non-cancerous) or they can go on to become cancerous. The type, size, and number of polyps that you have can affect your risk of developing colorectal cancer.
  • Medical conditions: Inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease, and diabetes have been associated with an increased risk of colorectal cancer. Rare genetic conditions like Lynch syndrome or familial adenomatous polyposis (FAP) are also linked to a higher risk of developing colorectal cancer.

Tests
When a person is diagnosed with colorectal cancer, that generally means they have malignant (cancerous) cells in the tissue of the colon and/or rectum. Doctors are able to make such a diagnosis by administering a variety of tests that analyze the rectum and rectal tissue as well as the blood. Catching colon cancer early with screening can greatly increase your survival. Common tests include:

  • Fecal occult blood test (FOBT): A sample of a person's stool is placed on a card, which is then examined under a microscope to see if there is blood in the stool, a sign of colorectal cancer. There are several factors that can give a falsely-positive FOBT, like consuming certain foods before the test.
  • Fecal immunochemical test (FIT): similar to FOBTs, a FIT checks your stool for blood. They are often preferred over FOBTs due to a lower risk of false positives from diet or medication-related factors, and are easier to use.
  • Digital rectal exam: A doctor or nurse examines the rectum with a lubricated, gloved finger to feel for any irregularities in the rectum or detect the presence of any polyps.
  • Colonoscopy: A colonoscope (a thin, lighted tube) is inserted into the rectum to provide doctors with a comprehensive view of a person's entire colon and the rectum. The doctors can also take out tissues or polyps (growths of tissue) so that they can be analyzed for a more complete diagnosis.
  • Biopsy: Cells or tissues are removed from the body for further examination under a microscope.
  • Flexible sigmoidoscopy: A sigmoidoscope (a thin, flexible tube with a camera on the end) is used to look inside a person's rectum and lower colon, also called the sigmoid. The sigmoidoscope checks for any abnormalities, including polyps and cancer.

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