Gene tests made by DeCode Genetics Inc., 23andMe Inc. and Navigenics Inc. add little that’s useful to what women learn about their risk for breast cancer from a family-history evaluation used for 20 years, a study found. Researchers from the National Cancer Institute and other institutions analyzed data from five long-running women’s health projects and performed gene tests on tissue samples women gave at the start of the studies. They found that the gene tests only “modestly improved” on the family-history method in predicting which women would develop breast cancer.

The finding suggests there are limits to what has been learned so far from the mapping of the human genome, completed a decade ago, according to an editorial accompanying the study today in the New England Journal of Medicine. Recent studies have also found that gene variants linked to diabetes and heart disease weren’t strong predictors of risk for the conditions, leading to “disappointment and caution,” wrote Dutch scientists Peter Devilee and Matti Rookus in the editorial.

“Based on these data, we don’t recommend that women seek genotyping as a means to better understand their personal risk profile,” said Patricia Hartge, deputy director of epidemiology and biostatistics at the cancer institute and one of the study authors. “We say that because in these data, there is just not a large benefit from adding that information. We’re still not at a level that translates into powerful enough predictions for clinical decision-making.”

Risk Questions

The standard method used today to evaluate a woman’s risk of developing breast cancer is a series of seven questions about her age, medical history and the history of cancer in her mother, sisters and daughters, Hartge said. Women can evaluate their own risk using an online version of the questionnaire on the cancer institute’s Web site.

The study tested the samples of 5,590 women in the study who developed breast cancer, as well as 5,598 who didn’t, looking for 10 common gene variants known as single nucleotide polymorphisms, or SNPs. Some of these variants are found in as many as 40 percent of all women, Hartge said in a telephone interview yesterday. Together these genes are thought to account for less than 5 percent of breast cancer risk, Devilee and Rookus said in their editorial.

The study didn’t look at mutations in the so-called breast cancer genes known as BRCA1 and BRCA2 that are found in fewer than 1 percent of women and are linked to a lifetime risk of breast cancer of 40 percent or higher.

Highest Risk Range

Kari Stefansson, president and chief executive officer of DeCode, the Icelandic gene-testing company that last year filed for bankruptcy protection, disagreed with the author’s conclusions. He said in a telephone interview today that the use of gene tests sold by his company can provide useful information for women who test in the highest ranges of risk.

“It gives you an opportunity to find a substantial increase in the number of women who end up in the high-risk category,” Stefansson said. “That is what you want to use this test for -- to find the women who are at truly high risk.”

The test can save women’s lives by warning those at high risk to be on the alert so they can be diagnosed early if they developed cancer, Stefansson said.

“Today, your prognosis from breast cancer is influenced more by how early it is diagnosed than anything else,” he said. Women whose cancer is found early, before it enters their lymph nodes, have a cure rate of almost 100 percent, he said.

Little Clinical Value

Navigenics, based in Foster City, California, and 23andMe, based in Carlsbad, California, include some of the 10 gene variants in gene tests they offer to the public. Both companies are closely held.

In their commentary, Devilee and Rookus agreed with the authors that testing for the 10 common gene variants is of little clinical value.

“For women seeking advice on their personal risk of breast cancer it is obviously too early to incorporate SNP testing into a counseling procedure, although such tests are already advertised for this purpose on the Internet,” they said. As new gene variants linked to breast cancer risk are discovered in the coming decade the value of such testing “will probably increase dramatically,” Devilee and Rookus said.