Wednesday, January 9, 2008

Breast-Cancer Genes May Pose Lower Risk

Women who carry certain gene mutations linked to increased breast-cancer risk may face less danger than previously believed, researchers said.

A study in this week's Journal of the American Medical Association estimates that women carrying mutations in one of two genes face a variable 40-51% risk of developing breast cancer by age 70, lower than the commonly cited 50%-80% risk. The study was sponsored by the National Cancer Institute.

The report comes amid a marketing push by Myriad Genetics Inc., a Salt Lake City company urging women with breast cancer in their family to know their risk by taking the company's test. Researchers didn't use the commercial test, but did independently test patients for mutations to BRCA1 and BRCA2 genes.

A Myriad spokesman said the company is familiar with past research from Colin Begg, who led the study. But despite his current assertions, the spokesman said, "We believe that high risk is high risk, whether 57% or 87%, and women should know in order to take the appropriate actions."

For the study, to be published in today's JAMA, researchers tested and interviewed about 1,400 women with cancer in one breast, and 700 women with cancer in both breasts who carried risky genes.

"The estimate of 50% to 80% breast-cancer risk from the gene is too high," said Dr. Begg, chairman of epidemiology and biostatistics at the Memorial Sloan Kettering Cancer Center in New York, adding that "even 40% may be an overestimate." Overestimates occur because studies focus on families with known cancer, rather than sampling unaffected families -- a huge and expensive undertaking, he said.

Despite a dearth of good prevalence data, Dr. Begg estimated that about one-half of 1%, or about 750,000 women in the U.S., carry the risky genes. The genes also are linked to ovarian-cancer risk. The JAMA study only looked at women with breast cancer, and relied on interviews with the women about their relatives' health status.

Women in the study faced higher risk if a relative's breast cancer was diagnosed at a young age or had occurred in both breasts. Risk varies as a result of lifestyle and environmental factors, as well as other breast-cancer genes.

Currently, BRCA1 and 2 testing is recommended for women with families already affected by cancer, rather than as a population-screening tool for women worried about breast cancer but not at risk.

Costing as much as $3,000, the test is generally covered by insurers if a woman has a family risk. But as technology advances and costs decline, Dr. Begg predicts broader screening will occur.

"My fear is once you're designated a carrier, you clue into this belief that your risk is high. My point is that, if we do population screening, we shouldn't be giving them that 80% [figure]," Dr. Begg said, adding that he has no ties to testing companies.

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