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New Study Finds Genetic Link Between Breast, Ovarian Cancers

July 7, 1998
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A new study has found that women who develop breast cancer because of a particular genetic mutation are 10 times more likely to also develop ovarian cancer than are breast cancer victims without the DNA defect.

The genetic mutations that can lead to breast cancer are more frequently found among Jewish women of Ashkenazi descent than among the general population.

The benefit of the new information, according to an executive at the genetic testing laboratory that underwrote the study, is that women who know they have a hereditary link to breast cancer can be carefully screened for indications of ovarian cancer, which is particularly deadly and difficult to detect in its early stages.

An estimated 10 percent of breast-cancer cases are believed to be linked to heredity. The causes of the other 90 percent are thought to be environmental, related to exposure to certain hormones and linked to diet and exercise.

Among American women in general, very few — just 2 percent — develop breast cancer before age 50. But between one-third and one-half of all women with a genetic mutation — Jews and non-Jews — will develop the disease before she turns 50.

By age 70, about 12 percent of women without the mutation, and between 56 and 87 percent of women with the mutation, get breast cancer, recent studies have shown.

A small percentage of women with the genetic mutation that predisposes them to get breast cancer — 10 percent — are Jews of Ashkenazi descent, meaning their ancestors came from Central or Eastern Europe.

But since Jews account for just about 2 percent of the American population, this disproportionate finding prompted alarm when the cancer-causing mutations on BRCA1 and BRCA2 were first identified about two years ago.

The purpose of the latest study was to find out which features of family history best predict mutations BRCA1 and BRCA2.

Determining the risk of ovarian cancer was not the study’s primary purpose, but the link quickly became apparent from the data, according to Dr. Tom Frank, medical director for Myriad Genetic Laboratories.

Myriad spent some $570,000 to conduct the analysis involved in the study. Based in Salt Lake City, Utah, Myriad is the only firm that currently offers the test for breast-cancer mutations commercially.

The link between genetic mutation and ovarian cancer was discovered by researchers from a dozen of the country’s leading medical institutions – – including the Sloan-Kettering Institute for Cancer Research in New York and the Anderson Cancer Center in Houston — who worked cooperatively with Myriad on the project.

The study examined 238 women with breast or ovarian cancer, or both, whose family histories showed a strong likelihood of genetic mutation.

Researchers found that women who had breast cancer but no genetic mutation developed ovarian cancer at the rate of under 2 in 1,000 women in the general population, which is about the same rate as that of women who have never had breast cancer, Frank said.

But with a genetic mutation, the incidence of ovarian cancer rose to over a 1 in 100 chance.

About 186,000 American women are diagnosed with breast cancer each year, and 44,000 women will die of the disease in the same period.

By contrast, some 26,000 women are diagnosed with ovarian cancer each year – – and half that number, 13,000, will die of the disease each year.

Dale Mintz, national director of health education for Hadassah, which has increasingly focused its attention on women’s health issues, was interested in news of the study, but questioned the source of the findings.

“I’d rather see large studies done by a university or the National Cancer Institute, because Myriad has a self-interest, and I’d rather see them done where they are pure science,” she said.

It costs an individual, or her insurance company, $2,400 for Myriad to do a full sequencing of the genes BRCA1 and BRCA2.

A search for mutations at the three points where they are most often found among Ashkenazi Jews costs $450, Frank said.

Frank acknowledged “we do have self-interest,” which is why he said his company cooperated with medical institutions.

“Anybody else doing this analysis using our methods would come up with exactly the same conclusions,” he said.

Mintz of Hadassah also expressed concern about potential discrimination by insurance companies against women who have found certain genetic mutations.

Frank said in the two years since Myriad began offering the breast cancer genetic testing, “I don’t think there’s a single report of a woman who had that test whose insurance was lost or who had her premium rates raised.”

But Mintz said there was reason for long-term concern.

If women do get tested and later become victims of the disease, “the insurance companies can say that they won’t pay for the surgical removal of cancerous breasts or ovaries” because the disease is considered a pre-existing condition, she said.

“It has not happened but the fear is there because there is no law yet preventing discrimination,” said Mintz, whose group is among those advocating for legislation to avoid such pitfalls.

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