Studies examine colorectal cancer screening rates

November 13, 2006

The rate of colorectal cancer screening appears to be increasing among Veterans Affairs patients, although use of colonoscopy is less common than other screening procedures, according to a report in the November 13 issue of Archives of Internal Medicine, one of the JAMA/Archives journals. A second report in the same journal shows that younger veterans with other illnesses and reduced life expectancies may not necessarily benefit from such screening and may even be harmed, but continue to be screened at high rates.

About 145,290 U.S. individuals developed colorectal cancer in 2005 and 56,290 died from the disease, according to background information in the first article. Screening for the disease has been shown to decrease illness and death. Methods include fecal occult blood testing (FOBT), which monitors for hidden blood in the stools, and colonoscopy, in which the large intestine (colon) is examined using a long flexible instrument known as a colonoscope. "Because it is the most invasive and costly approach and because it is usually performed by specialists, until recently, colonoscopy was primarily used to screen high-risk individuals, for diagnostic purposes or to follow up on abnormal results of other screening tests," the authors write. However, because it can examine the whole colon and remove potentially cancerous growths at the same session, colonoscopy is increasingly common as indicated by data from Medicare and other health care systems and is recommended as the most accurate screening tool by a growing number of professional organizations.

Hashem B. El-Serag, M.D., M.P.H., of the Michael E. DeBakey VA Medical Center and Baylor College of Medicine, Houston, and colleagues studied screening patterns in patients who received care in the Department of Veterans Affairs between 1998 and 2003. By searching national inpatient and outpatient VA databases, the researchers identified all patients age 49 to 75 who had undergone FOBT, colonoscopy, a test known as flexible sigmoidoscopy, or double contrast barium enema, another screening method that involves taking X-rays of the colon and rectum.

A total of 5,125,938 screening tests for colorectal cancer were performed on 2,402,657 patients between 1998 and 2003--an average of 2.1 procedures per patient. The number of tests increased from 432,778 in 1998 to 1,179,764 in 2003. Also in that time period, the proportion of FOBT tests increased from 81.7 percent to 90.4 percent; screening colonoscopy declined from 5.7 percent to 4.7 percent; flexible sigmoidoscopy declined from 8.3 percent to 3.6 percent; and double contrast barium enema declined from 4.1 percent to 1.3 percent.

Although the number of screening colonoscopies performed during that time increased from 24,955 to 55,199, the percentage of colonoscopies used for screening rather than diagnostic or other purposes increased only slightly, from 34.3 percent to 38.4 percent. "Although screening colonoscopy more than doubled in frequency, it still constitutes a small proportion of colorectal cancer screening," the authors write. "Overall, there was no significant difference in the likelihood of undergoing screening colonoscopy between 1998 and 2003."

FOBT has been criticized for its lack of ability to correctly identify those with and without colorectal cancer, they continue. "Apart from the advantages of colonoscopy ... the effectiveness of an FOBT-based screening program in clinical settings (as opposed to clinical trials) is unclear. The predominant use of FOBT for colorectal cancer screening in the VA, while strikingly different from other health care systems in the United States, may not necessarily lead to worse outcomes in terms of colorectal cancer-related incidence and mortality. It does, however, call for closer examination of the process and outcomes of this practice in VA settings."

In the second study, Shahnaz Sultan, M.D., then at Duke University Medical Center and Durham Veterans Affairs Medical Center, North Carolina, and now at University of Florida College of Medicine, Gainesville, and colleagues examined the relationship between colorectal cancer screening, health status and other illnesses in 861 patients treated at a single VA Medical Center between 1996 and 2004. The participants were age 50 to 64 with no history of colorectal cancer or screening. Each patient completed two surveys about their health and comorbid (co-occurring) illnesses; data about screening were collected from hospital and individual medical records.

Within five years of their initial clinic visit, 395 (45.9 percent) of the veterans underwent screening for colorectal cancer, including 258 (65.3 percent) who had FOBT and 138 (34.9) who had a colonoscopy. Researchers separated patients into groups by age and health status, with three groups for age (50 to 54, 55 to 59, and 60 to 64), three for comorbid diseases (no or mild, moderate, or severe) and four for health status (with one being the worst and four being the best). High screening rates were observed for patients with poor health scores and co-occurring illnesses. This included 84 of 187 (44.9 percent) of those with moderate illness and 55 of 120 (45.8 percent) of those with severe illness, as well as 88 of 216 (40.7 percent) of those with the worst health scores.

For a screening test to be beneficial, it must reduce the rates of patients who die from the disease they are screened for and prolong the life expectancy of those who are screened, the authors write. "In the context of colorectal cancer screening, if an individual's life expectancy is anticipated to be fewer than five years, then screening may be of little benefit," they continue. "In our study, 52 patients died during the five-year follow-up period from non-colorectal cancer deaths, and of these patients, 71.2 percent had undergone colorectal cancer screening but had not derived any survival benefit. Most of these individuals had limited life expectancy based on their health status and comorbidity score and may, therefore, have been inappropriately screened."

"Future research should focus on the development of appropriate decision tools to reduce potentially inappropriate colorectal cancer screening in severely chronically ill patients," the authors conclude.
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(Arch Intern Med. 2006;166:2202-2208 and 2209-2214. Available pre-embargo to the media at www.jamamedia.org.)

Editor's Note: Please see the articles for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Editorial: Limited Resources Strain Screening Programs

Although screening for colorectal cancer has been shown to reduce death and the occurrence of the disease, screening rates still lag behind those for breast and prostate cancer patients, write Hemant K. Roy, M.D., Evanston-Northwestern Healthcare, Illinois, and colleagues in an accompanying editorial.

Medicare coverage and high-profile endorsements have increased interest in colonoscopies, the most accurate screening method, they write. "The increased success of these public awareness campaigns has raised an important issue--the insufficient health care resources to meet the needs. For instance, if colonoscopies were actually performed on the entire population of more than 70 million Americans older than 50 years, the annual costs would exceed $10 billion. Moreover, many estimates suggest that entire population screening would exceed existing endoscopic capacity."

Targeting high-risk patients for colonoscopies and effectively using other screening methods for the rest of the population, as well as working to develop additional tests that could separate patients by risk level, will help physicians efficiently use the screening resources available, they conclude.

(Arch Intern Med. 2006;166:2177-2179. Available pre-embargo to the media at www.jamamedia.org.)

Editor's Note: Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

For more information, contact JAMA/Archives Media Relations at 312/464-JAMA (5262) or e-mail mediarelations@jama-archives.org.

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