AHCPR Releases Evidence Report on Colorectal Cancer Screening

In late January, the Agency for Health Care Policy and Research (AHCPR)released the first evidence report under its new evidence-based practiceinitiative. The report indicates that screening has been shown to be effectivein detecting early-stage colorectal cancers and their precursors. Earlydetection and treatment are the primary means of preventing deaths fromcolorectal cancer.

Colorectal cancer is the third most commonly diagnosed cancer in theUnited States and the second leading cause of cancer death. It is estimatedthat in 1996, 133,500 new cases of colorectal cancer were diagnosed, andthat colorectal cancer accounted for 54,900 deaths.

"This evidence report will improve the early detection and treatmentof colorectal cancer by giving clinicians and others state-of-the-art informationon screening and diagnostic tests to help them reduce the mortality fromthis deadly disease," said AHCPR administrator Clifton R. Gaus. "Ourgoal is to make this information, and all the evidence reports releasedin the future, available in the public domain to the widest audience possible."

The evidence-based practice initiative, established in October 1996,will provide medical societies, health-care systems, purchasers, healthplans, and others with a scientific foundation for developing and implementingtheir own clinical practice guidelines, performance measures, and otherquality improvement tools. In December 1996, the AHCPR issued a requestfor proposals to fund evidence-based practice centers to produce futureevidence reports and also published a notice in the Federal Registerinviting nominations for report topics.

Findings of the Evidence Report

The Colorectal Cancer Screening Evidence Report is based on a systematicreview of 3,500 citations from the scientific literature published between1966 and 1994. The review found evidence that a reduction in deaths fromcolorectal cancer can be achieved through the detection and treatment ofearly-stage colorectal cancers and the identification and removal of adenomatouspolyps--the precursors of colorectal cancers. Other findings include:

Colorectal cancer incidence rises with age, beginning around age 40,and is higher in men than in women (60.4 vs 40.9 per 100,000 per year).

Survival from colorectal cancer is closely related to the clinical andpathologic stage of the disease at diagnosis. Up to 90% of patients withcancer limited to the bowel wall will be alive 5 years after diagnosis,as compared with 35% to 60% of those with involvement of the lymph nodes,and less than 10% of patients with metastatic disease.

Racial differences in colorectal cancer survival have been observed.The 1983 to 1989 5-year relative survival rate for colon cancer was 61%among white men, 50% among white women, 48% among African-American men,and 49% among African-American women. African-American men and women withcolorectal cancer have a 50% greater probability of dying of colon cancerthan do white men and women.

Well-established risk factors for colorectal cancer include older age,male sex, history of inflammatory bowel disease, certain hereditary conditions,and a family history of colorectal cancer. However, about 75% of all colorectalcancer occurs in people with no known risk factors.

Most Americans are not screened for colorectal cancer. More than two-thirdsof patients present with advanced disease. Information from the NationalHealth Interview Survey (NHIS) indicates that in 1992, only 17.3% of peopleage 50 and older had undergone fecal occult blood testing in the previousyear, and 9.4% had undergone sigmoidoscopy in the previous 3 years.

Screening with fecal occult blood testing has been shown to reduce colorectalcancer mortality. Screening with flexible sigmoidoscopy can reduce colorectalcancer mortality risk, but clinical trials have not been performed thatdirectly assess mortality reduction.

Double-contrast barium enema and colonoscopy are proven methods of identifyingpolyps and colorectal cancer but have not been studied as screening tests.

Further research is needed to demonstrate the effectiveness of colorectalcancer screening tests and determine optimal intervals for such testing.

New AGA Clinical Practice Guideline

The information contained in the AHCPR's evidence report is the basisfor a clinical practice guideline on colorectal cancer screening by theAmerican Gastroenterology Association (AGA) that was published in the Februaryissue of Gastroenterology. The AGA led a consortium that directed an AHCPR-sponsoredclinical practice guideline panel on colorectal cancer screening. Workon the AHCPR-sponsored guideline was discontinued when the agency endedits clinical practice guide- line program and began developing evidencereports. The AGA then decided to sponsor its own science based guidelineon colorectal cancer screening.

"AGA's use of this information on colorectal cancer screening todevelop its guideline on colorectal cancer screening demonstrates the importanceand potential impact of AHCPR's Evidence-Based Practice Initiative,"noted Dr. Gaus."AHCPR is filling a need for comprehensively reviewed,rigorously analyzed science sought by public- and private-sector organizationsto use in improving the quality of health-care services they provide."

An executive summary of the Evidence Report on Colorectal Cancer Screeningis available on AHCPR's World Wide Web site (http://www.ahcpr.gov/), fromAHCPR's Publications Clearinghouse at (800) 358-9295, and from AHCPR'sInstant Fax, (301) 594-2800. The complete evidence report will be availablein the near future.