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Colonoscopy screening has reduced incidence of colorectal cancer

Robin Wulffson MD's picture
colonoscopy, cancer screening, colon cancer, colorectal cancer

Colonoscopy is the most commonly employed screening method for colorectal cancer (CRC) in the United States. Researchers affiliated with Stanford University conducted a study to determine whether the procedure would reduce the incidence of new colorectal cancers. They published their findings in the November issue of the journal Gastroenterology.

The researchers examined United States trends in rates of resection for proximal vs. distal CRC, which reflect CRC incidence, in the context of national CRC screening data, before and since Medicare's 2001 decision to pay for screening colonoscopy. Proximal CRC refers to the upper portion of the colon (cecum, ascending colon, and transverse colon); distal CRC refers to the lower portion of the colon (descending colon, sigmoid colon, rectosigmoid, and rectum)).

The study comprised data from more than 2 million patients collected from 1993 to 2009. The researchers used the Nationwide Inpatient Sample, which is the largest US all-payer inpatient database, to estimate age-adjusted rates of resection for distal and proximal CRC in adults. They found that the rate of resection for distal CRC decreased from 38.7 per 100,000 persons to 23.2 per 100,000 persons from 1993 to 2009, with annual decreases of 1.2% from 1993 to 1999, followed by larger annual decreases of 3.8% from 1999 to 2009. In contrast, the rate of resection for proximal CRC decreased from 30.0 per 100,000 persons to 22.7 per 100,000 persons from 1993 to 2009; however, significant annual decreases of 3.1% occurred only after 2002. Rates of resection for CRC decreased for adults ages 50 years and older; however, the rates increased for younger adults.

The authors concluded that their findings support the hypothesis that population-level decreases in rates of resection for distal CRC are associated with screening, in general, and that implementation of screening colonoscopy, specifically, might be an important factor that contributes to population-level decreases in rates of resection for proximal CRC.

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Colon cancer screening:
Colon cancer screening can detect polyps and early cancers. Such screening can detect changes that can be treated before symptoms develop. Regular screenings may decrease deaths and prevent pain caused by colorectal cancer. Several tools may be used, either alone or in combination, to screen for colon cancer:
The first method is stool tests that examine your bowel movements to check for blood. Polyps in the colon and smaller cancers often cause small amounts of bleeding that cannot be seen with the naked eye. The most common one used is the fecal occult blood test (FOBT). Newer stool tests are called the fecal immunochemical test (FIT) and stool DNA test (sDNA).
The second method is a sigmoidoscopy exam. This test uses a flexible small scope to look at the lower part of your colon. Because it only looks at the last one-third of the large intestine (colon), it may miss some cancers. Most healthcare providers recommend that the stool test and sigmoidoscopy be used together.
The third method is a colonoscopy exam. A colonoscopy is similar to a sigmoidoscopy, but it allows the entire colon to be viewed. You will usually be mildly sedated during a colonoscopy.

Screening recommendations for average-risk individuals:

  • There is not enough evidence to determine which screening method is best. Discuss with your doctor which test is most appropriate for you.
  • Beginning at age 50, both men and women should have a screening test. Some healthcare providers recommend that African Americans begin screening at age 45.

Screening options for patients with an average risk for colon cancer:

  • Colonoscopy every 10 years.
  • Double-contrast barium enema every 5 years.
  • Fecal occult blood test (FOBT) every year - if results are positive, a colonoscopy is needed.
  • Flexible sigmoidoscopy every 5 - 10 years, usually with stool testing FOBT done every 1 - 3 years.
  • Virtual colonoscopy every 5 years. Virtual colonoscopy combines MRI or CT scans with sophisticated computer software to produce three-dimensional images of the colon and rectum. The test is less invasive than conventional colonoscopy; however, it does involve exposure to ionizing radiation.
  • A test called capsule endoscopy (swallowing a small, pill-sized camera) is also being studied, but it is not yet recommended for standard screening at this time.

People with certain risk factors for colon cancer may need earlier (before age 50) or more frequent testing. More common risk factors are:

  • A family history of inherited colorectal cancer syndromes, such as familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC).
  • A strong family history of colorectal cancer or polyps. This usually means first-degree relatives (parent, sibling, or child) who developed these conditions younger than age 60.
  • A personal history of colorectal cancer or polyps.
  • A personal history of chronic inflammatory bowel disease (for example, ulcerative colitis or Crohn's disease).

Reference: Gastroenterology