The proportion of relatives willing to undergo testing nearly halved after they took part in group discussion sessions on the subject.
Relatives were deterred by the cost of screening tests, and by fear of the implications of getting a positive test result.
Writing in the journal Cancer, researchers told how they enrolled 28 patients and 33 first-degree relatives to take part in the sessions.
Before the sessions 82 per cent of relatives intended to undergo testing - but after talking it through with others, the proportion dropped to 42 per cent.
Those favoring genetic testing, before and after discussion sessions:
Patients - 96 vs. 89 %
Relatives - 82 vs. 42 %
Cancer patients themselves were overwhelmingly convinced of the benefits of testing. The proportion favoring it only fell from 96 per cent to 89 per cent after the discussions.
The relatives, all North American, admitted being put off testing when told it would cost 2,500 dollars. Most had not expected to pay more than 100 dollars.
Researcher Anita Kinney, of the University of Utah College of Nursing, Salt Lake City, USA, said, "Our data suggests that concerns about genetic discrimination may prompt individuals at increased risk to avoid genetic tests that could have potential health benefits."
She added, "Despite a general lack of knowledge about genetic testing for familial colorectal cancer, patients and first-degree relatives clearly regard genetic issues - and the direct implications of these issues on their lives - as extremely important."
Report Copyright: Englemed Health News at http://www.internationalmedicalnews.com