Changes from the 2002 guidelines include recommendations not to routinely screen people over 75 and not to screen people over 85 at all. Decisions about screening between 76 and 85 need to be made in light of individual health, prior screening, and life expectancy.
The recommendations have dropped barium enema as a screening option. They do not include either CT colonography (CTC or so-called virtual colonoscopy) or DNA stool tests, saying that there was not enough current evidence to judge the harms and benefits of the new technology.
In summarizing their recommendations, the USPSTF points out,
The likelihood that detection and early intervention will yield a mortality benefit declines after age 75 because of the long average time between adenoma development and cancer diagnosis.
Screening for Colorectal Cancer: USPSTF 2008 Recommendations
- The USPSTF recommends screening for colorectal cancer usingfecal occult blood testing, sigmoidoscopy, or colonoscopy inadults, beginning at age 50 years and continuing until age 75. This is an A recommendation. (There is a high certainty that net benefit is substantial.)
- The USPSTF recommends against routine screening for colorectalcancer in adults age 76 to 85 years. There may be considerations that support colorectal cancer screening in an individual patient. This is a C recommendation. (There is moderate or high certainty that the net benefit is small.)
- The USPSTF recommends against screening for colorectal cancer in adults older than age 85 years. This is a D recommendation. (There is moderate or high certainty that the service has no benefit or that harms outweigh the benefits.)
- The USPSTF concludes that the evidence is insufficient to assessthe benefits and harms of computed tomographic (CT) colonographyand fecal DNA testing as screening modalities for colorectalcancer. This is an I statement. (…current evidence is insufficient to assess the balance of benefits and harms of the service.)
Analyses that led to the new guidelines found three strategies equally effective in reducing deaths from colorectal cancer for people of average risk without symptoms if they were followed consistently:
- Colonoscopy every 10 years beginning at age 50 and ending at age 75.
- High sensitivity fecal occult blood testing every year.
- Flexible sigmoidoscopy every 5 years with a high-sensitivity fecal occult blood test every 3 years.
Two strategies that were less effective and not recommended were
- Flexible sigmoidoscopy every 5 years without an intervening FOBT.
- Annual FOBT using a low-sensitivity test.
Fecal occult blood tests look for blood in the stool. High-sensitivity fecal occult blood tests in the supportive studies for the recommendations were the Hemoccult SENSA guaiac testing and fecal immunohistochemical tests (FIT). Hemoccult II guaiac testing was considered to be low in sensitivity.
For their recommendations, the USPSTF depended on two computer simulation models that took into account existing information about colorectal cancer and its progression from adenomatous polyps. MISCAN and SimCRC modeled the number of life-years gained using several different screening strategies. They also estimated the number of colonoscopies, with accompanying risks, that would be necessary to carry out each strategy.
The USPSTF did look at data that considered the risks and benefits of beginning screening earlier than age 50 and concluded,
For all screening modalities, starting screening at age 50 resultedin a balance between life-years gained and colonoscopy risksthat was more favorable than commencing screening earlier.
In considering CT colonography, USPSTF was concerned about potential radiation hazards over a lifetime of use and the fact that CTC can uncover suspicious lesions outside the colon that then require invasive procedures to evaluate even if they eventually prove harmless.
In the USPSTF’s opinion, fecal DNA technology is still evolving and there is not sufficient evidence to make a recommendation for its use.
Barium enema was not included in the updated recommendations because of its lower sensitivity, the fact that it has not been part of screening trials, and its use as a screening method is declining in the US.
In March of 2008, the American Cancer Society, Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology issued joint guidelines for Screening and Surveillance for the Early Detection of Colorectal Cancer and Adenomatous Polyps. The joint guidelines do endorse both CT colonography (CTC) for the detection of adenomatous polyps and stool DNA to find colon cancer early.
SOURCES: Screening for Colorectal Cancer: U.S. Preventive Services Task Force Recommendation Statement, Annals of Internal Medicine, Volume 149, Number 9, November 4, 2008.
Zauber et al., Evaluating Test Strategies for Colorectal Cancer Screening: A Decision Analysis for the U.S. Preventive Services Task Force, Annals of Internal Medicine, Volume 149, Number 9, November 4, 2008.
The Annals of Internal Medicine includes a summary for patients of the new USPSTF recommendations.