In late January, the Agency for Health Care Policy and Research (AHCPR)
released the first evidence report under its new evidence-based practice
initiative. The report indicates that screening has been shown to be effective
in detecting early-stage colorectal cancers and their precursors. Early
detection and treatment are the primary means of preventing deaths from
Colorectal cancer is the third most commonly diagnosed cancer in the
United States and the second leading cause of cancer death. It is estimated
that in 1996, 133,500 new cases of colorectal cancer were diagnosed, and
that colorectal cancer accounted for 54,900 deaths.
"This evidence report will improve the early detection and treatment
of colorectal cancer by giving clinicians and others state-of-the-art information
on screening and diagnostic tests to help them reduce the mortality from
this deadly disease," said AHCPR administrator Clifton R. Gaus. "Our
goal is to make this information, and all the evidence reports released
in 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, health
plans, and others with a scientific foundation for developing and implementing
their own clinical practice guidelines, performance measures, and other
quality improvement tools. In December 1996, the AHCPR issued a request
for proposals to fund evidence-based practice centers to produce future
evidence reports and also published a notice in the Federal Register
inviting nominations for report topics.
Findings of the Evidence Report
The Colorectal Cancer Screening Evidence Report is based on a systematic
review of 3,500 citations from the scientific literature published between
1966 and 1994. The review found evidence that a reduction in deaths from
colorectal cancer can be achieved through the detection and treatment of
early-stage colorectal cancers and the identification and removal of adenomatous
polyps--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 and
pathologic stage of the disease at diagnosis. Up to 90% of patients with
cancer 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 with
colorectal cancer have a 50% greater probability of dying of colon cancer
than 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 colorectal
cancer occurs in people with no known risk factors.
Most Americans are not screened for colorectal cancer. More than two-thirds
of patients present with advanced disease. Information from the National
Health Interview Survey (NHIS) indicates that in 1992, only 17.3% of people
age 50 and older had undergone fecal occult blood testing in the previous
year, and 9.4% had undergone sigmoidoscopy in the previous 3 years.
Screening with fecal occult blood testing has been shown to reduce colorectal
cancer mortality. Screening with flexible sigmoidoscopy can reduce colorectal
cancer mortality risk, but clinical trials have not been performed that
directly assess mortality reduction.
Double-contrast barium enema and colonoscopy are proven methods of identifying
polyps and colorectal cancer but have not been studied as screening tests.
Further research is needed to demonstrate the effectiveness of colorectal
cancer 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 basis
for a clinical practice guideline on colorectal cancer screening by the
American Gastroenterology Association (AGA) that was published in the February
issue of Gastroenterology. The AGA led a consortium that directed an AHCPR-sponsored
clinical practice guideline panel on colorectal cancer screening. Work
on the AHCPR-sponsored guideline was discontinued when the agency ended
its clinical practice guide- line program and began developing evidence
reports. The AGA then decided to sponsor its own science based guideline
on colorectal cancer screening.
"AGA's use of this information on colorectal cancer screening to
develop its guideline on colorectal cancer screening demonstrates the importance
and 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 organizations
to use in improving the quality of health-care services they provide."
An executive summary of the Evidence Report on Colorectal Cancer Screening
is available on AHCPR's World Wide Web site (http://www.ahcpr.gov/), from
AHCPR's Publications Clearinghouse at (800) 358-9295, and from AHCPR's
Instant Fax, (301) 594-2800. The complete evidence report will be available
in the near future.