Public Release: 

Use of genetic testing for colorectal cancer may increase screening rates

More targeted training on screening recommendations needed

American Association for Cancer Research

Boston, MA (October 17, 2002) - Individuals with a genetic predisposition for colorectal cancer (CRC) were more likely to be screened for the disease, according to a study presented at the American Association for Cancer Research's (AACR) first annual Frontiers in Cancer Prevention Research meeting. Those carrying the gene alteration were significantly more likely to undergo a colonoscopy (70 percent), compared to those who did not carry the risk-conferring gene alteration (22 percent) and individuals who declined testing (16 percent).

HNPCC is the most common form of inherited colon cancer, and affects at least one person per thousand. People with the HNPCC genetic mutation are encouraged to undergo colonoscopy screening every one to two years.

"Previous studies have indicated that genetic test results have a limited impact on cancer screening behavior," according to Chanita Hughes, Ph.D., assistant professor of psychiatry at the University of Pennsylvania, Philadelphia, and lead investigator of the study. "We were pleased our study found that the results of an HNPCC genetic test may actually motivate colonoscopy screening among those who test positive."

HNPCC is a condition that increases the risk of developing colon cancer and can be detected by genetic testing. Mutations in at least four genes are linked to HNPCC, and an estimated five to 10 percent of all colon cancer cases are believed to result from these mutations. People who carry one or more of the mutations have an 80 to 85 percent risk of developing colorectal cancer by age 75. Colon cancer resulting from HNPCC is diagnosed in people around age 45 (sometimes in people still in their 20s) - much earlier than non-inherited forms of colon cancer.

Between 43 to 76 percent of high-risk individuals undergo genetic testing for colorectal cancer. There are three familial factors that determine whether patients should undergo genetic testing for colorectal cancer: three cases of rectal cancer or other HNPCC-associated cancers; illnesses spread over at least two generations; and at least one cancer patient diagnosed before age 50.

Education on Colorectal Cancer Screening Needed in Underserved Communities

In another study presented at the AACR meeting, researchers identified the vital need to train physicians, particularly in underserved communities, about the importance of regular screening for colorectal cancer. The study, which was conducted by researchers at Columbia University, New York, showed that colonoscopy was significantly more common in affluent and white communities than was fecal occult blood test (FOBT), and that salaried physicians were less likely to use the FOBT for colorectal cancer screening than were other primary care physicians.

"Our study was designed to assess the effect of community, race/ethnicity, income and primary care physician characteristics on colorectal cancer screening," according to Sherri N. Sheinfeld Gorin, Ph.D., an assistant professor of sociomedical sciences and epidemiology, Mailman School of Public Health, Columbia University, and lead investigator of the study. "We found that primary care physicians who were more accurate in their identification of risk factors for colorectal cancer were more likely to periodically screen older patients in their practice than other physicians seeing similar patients."

The study found that primary care physicians were most likely to periodically screen patients age 50 or over using the FOBT (75 percent) or colonoscopy (71 percent). Forty-six percent of these urban physicians used the flexible sigmoidoscopy periodically to detect colorectal cancer; 11 percent conducted the procedure themselves. Less common was periodic screening using the flexible sigmoidoscopy and FOBT (37 percent), or the double contrast barium enema (4 percent). Eighty-six percent of the physicians obtained a stool sample with a digital rectal exam for screening, contrary to recommended practices. One-half of the PCP's had been in practice 14 years or more, working in busy offices (average 86 contacts per week, standard deviation, 48). Only two percent correctly identified five major risk factors for colorectal cancer.

More than 148,000 new cases of colorectal cancer will be diagnosed, and more than 56,000 people will die in 2002, according to the American Cancer Society. An individual's lifetime risk of developing colorectal cancer is nearly six percent, with over 90 percent of cases occurring after age 50. Many of the new cases and deaths from colorectal cancer are preventable by improvements in nutrition and physical activity, and by timely use of existing colorectal cancer screening tests.

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Founded in 1907, the American Association for Cancer Research (AACR) is a professional society of more than 19,000 laboratory and clinical scientists engaged in cancer research in the United States in more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals (Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention).

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