Experts question new DNA test for breast cancer risk

Experts question new DNA test for breast cancer risk

By Judy Peres
Tribune staff reporter
Published October 22, 2006

In what could be the leading edge of a new and controversial wave of genetic tests, some women are beginning to get their DNA sampled to reveal their odds of developing breast cancer. The test doesn't check for mutations in the rare BRCA genes that dramatically increase cancer odds--which is often recommended for families with a lot of breast or ovarian cancer. Rather, it looks for more common genetic variations that its developers say occur more frequently in breast cancer patients than in healthy women. The producers of such tests argue they help identify people more likely to get a disease and allow them to take action to reduce their risk. But experts say finding an association between genetic variations, or polymorphisms, and breast cancer is only the first of many steps needed to show that those variations can predict risk in healthy women. Risk prediction tests based on DNA analysis are the newest development in a rapidly growing field. Genetic screenings--many available over the Internet--range from tests for genes known to cause specific diseases to pseudoscientific products that claim to tell consumers which nutritional supplements will keep them healthy.

Critics say some companies are exploiting consumers' anxiety to sell them expensive tests they don't need--products that cater to the "worried well" who can afford to pay. An Oklahoma company called InterGenetics Inc. was set to start selling its OncoVue breast cancer risk test last spring for $647 before the Food and Drug Administration stepped in to demand further testing. After months of talks, the firm now has approval to sell the test at a discounted rate to 12,000 women as part of a study. One of the first to be tested in the Chicago area was Charmaine Ghidara of Streamwood, who said she feared she was at increased risk for cancer and wanted to know if she should take the preventive drug tamoxifen. "I don't want to," said Ghidara, 57. "But I'm worried I might be prone to getting breast cancer."

To take the OncoVue test, a woman swishes some mouthwash and then spits into a tube, which is sent to the company's laboratory in Oklahoma City. There, DNA from the woman's cheek cells is isolated for analysis. The testers are looking for genetic variations called SNPs that the company identified in a study of about 8,000 women with and without breast cancer. Pronounced "snip," SNP stands for single nucleotide polymorphism. After adding in other known risk factors, such as age and number of close relatives with the disease, a computer calculates the woman's chances of getting breast cancer. The risk is displayed as an absolute percentage and also in comparison to the average risk of women in her age group.

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