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April 10, 1999

Regardless of Their Risk of Colon Cancer, Most Would Undergo Genetic Screening

A scientific survey of people having one or more close relatives with colon cancer has found that those without significant family histories of the disease were just as eager to undergo gene testing for colon cancer as those with multiple affected relatives, even though most knew little or nothing about gene testing for colon cancer. The study appeared in the April issue of Cancer Epidemiology, Biomarkers & Prevention.

Lead author Gloria M. Petersen, PhD, associate professor, Epidemiology, Johns Hopkins School of Public Health, said, "Surprisingly, interest in gene testing was high regardless of the number of relatives with colon cancer. And whereas 70.3 percent this group had not read or heard much about colon cancer gene testing, the vast majority--92.4 percent--said they would be likely or very likely to take the test."

A total of 1518 persons with one or more relatives with colon cancer completed and returned a 30-page survey that asked about their perceptions of their risk and their attitudes toward colon cancer gene testing. The researchers also randomly telephoned 200 people who had not completed the survey and asked them about their interest in genetic testing.

The study showed that in spite of the fact that colon cancer risk is increased two- to three-fold in persons with a family history of colon cancer, and many of those surveyed were aware of their increased risk of colon cancer, most rarely thought about their elevated risk. Twenty-two percent of those surveyed said they were unaware of their increased risk of colon cancer. Eight percent expressed no concern about developing colon cancer; 4.8 percent felt their chance of developing the disease was lower than others of the same age, sex, and race; and 3.3 percent felt they were very unlikely to develop colon cancer in their lifetime. Most, however, were eager to undergo genetic testing.

The researchers said that the lack of any relationship between the strength of one's family history for colon cancer and one's willingness to receive genetic testing may be an advantage, since people with a family history of the disorder are recommended to undergo colon screening at an earlier age than the general population, and such persons may benefit from educational and genetic counseling alone.

Dr. Petersen said, "It is of concern that there were individuals surveyed who were at much greater risk of colon cancer but who perceived their risk as the same or lower than others of the same age, sex, and race. It will be important to identify the factors, whether psychological, medical, or social, that shape this lowered risk perception."

This study was supported in part by a grant from the National Institutes of Health and the Clayton Fund.

Public Affairs Media Contacts for the Johns Hopkins Bloomberg School of Public Health: Tim Parsons or Kenna Brigham @ 410-955-6878 or paffairs@jhsph.edu