Families do not understand the implications of genetic test results

Major study links two new genetic variants to breast cancer
Major study links two new genetic variants to breast cancer

Many relatives of patients who undergo testing for genetic links to breast and ovarian cancers misinterpret the results, and less than half of those who could benefit from genetic testing say they plan to undergo testing themselves, according to a recent study. This is despite the fact that knowing your genetic status may help detect the disease in its earliest stages. The study results were presented at the 2013 San Antonio Breast Cancer Symposium, December 10-14, 2013.

"People don't always understand genetic information, so there's confusion," said study author Mary B. Daly, MD, PhD, of Fox Chase Cancer Center in Philadelphia, Pennsylvania. "Family members are either not understanding what they're hearing, not realizing it has implications for them, or they're not hearing it at all."

Daly said she naively assumed, for a long time, that once one family member knew whether or not they were carriers of the BRCA1/2 genes their entire family understood the results, and what it meant for their own genetic risk. "Over time, we realized that wasn't happening, or it wasn't happening very well."

Some genetic information is straightforward, explained Daly. For example, when a woman learns she carries BRCA1/2 that means her parents, siblings, and children may also carry the gene. But there are more indeterminate results, which are harder to interpret, she added. If a woman with a strong family history of breast and ovarian cancers tests negative for the BRCA1/2 genes, that does not mean her relatives are not at risk—her siblings could still carry the gene, or there could be additional genes present that predispose them to cancer that clinicians do not yet know how to test for.

"When you look at some of these families who are so full of breast and ovarian cancer, and the person tests negative, you think there's got to be something going on here. We just can't find it. That's a difficult thing for someone to explain to a relative," said Daly.

To understand better what was (and was not) being communicated after people underwent genetic testing, Daly and her team called 438 relatives of 253 people who had undergone genetic testing and reported sharing their results with their families. More than one-quarter of family members reported the test result incorrectly. They were most likely to understand positive results—such as their family member carries the BRCA1/2 gene. But only 60% understood the indeterminate results, where their relative tested negative for the gene but they and other family members could still be at risk. Nearly one-third said they had trouble understanding the result.

Of concern was that only half (52%) of family members whose relative tested positive for the BRCA1/2 gene said that they planned to undergo testing themselves. Among those whose relative tested negative for the BRCA1/2 gene, but knew the gene was present in their families (meaning they could still carry the gene), only 36% said they were going to find out their own genetic risk.

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