Women's genes and heritage reveal cancer risk

After reading about a research study to test genetic mutations that can increase the risk of breast cancer in Jewish women back in May 2008, Marsha Moshinsky signed up immediately. “I want to know if I, and therefore possibly my children, carry these mutated genes,” she wrote in her journal that day. “If I am a carrier, I want to face the risks head on, with as much knowledge as possible and with preventive treatment at my disposal.”

The results of that study, which tested more than 2,000 women, were published in December 2009 in the Journal of Clinical Oncology. The findings: Just over one per cent of Jewish women in Ontario carry the mutated BRCA1 or BRCA2 genes -- about four times higher than the general population. The mutated gene means carriers have an 80 per cent risk of developing breast cancer and up to a 40 per cent risk of developing ovarian cancer.

Shocked by the results
Of those who tested positive, more than half were ineligible for testing according to provincial guidelines, which are similar across the country and in the United States. To be qualified for screening, you must have a history of breast or ovarian cancer or a strong history of these diseases in your family.

“We were surprised by the lack of family history,” says lead author Kelly Metcalfe, adjunct scientist at Women’s College Research Institute. “The women getting the results were very shocked as well. There had been nobody in their family with cancer, and we don’t often observe BRCA 1 or 2 mutations in families without significant histories of breast and ovarian cancer.”

Additionally, 45 per cent of the women with a mutated gene were eligible for testing but were never referred by their physicians. “I think it’s probably because the majority of the mutations were coming from the father’s side,” Metcalfe explains. “There is this misunderstanding out there that breast cancer risk can’t be inherited through a father. That’s false. It’s just as likely to come from the father’s side as it is the mother’s side.”

More testing offered
The Ontario researchers expect the results would be similar across the country. French Canadian women are also genetically predisposed to the mutations, which Metcalfe explains as “common founder mutations.” In both ethnicities, she says “the population stays together so those mutations don’t get filtered out over generations.” They hope this study demonstrates the need to screen based on genetic predisposition and not just family history.

But the researchers aren’t waiting for the government to realize guidelines should be changed, though they will do a formal economic evaluation for provincial review. With the published paper came an announcement: A new round of testing is being offered, for up to 5,000 women.

“It really wasn’t a research question,” says Metcalfe. “We know a lot of these women who have mutations wouldn’t have been eligible for genetic testing based on the current provincial guidelines, so what do we do about this? For us, it’s something we feel we need to do for the Jewish population. We need to offer this testing when we know that so many mutations would be observed in people who wouldn’t have been qualified to have this testing done clinically.” About 2,200 women signed up the first day.

Know your family history, understand your risks
Although Moshinsky received a letter that revealed her genetic test for the mutated gene was negative and her risk of developing breast or ovarian cancer was no greater, she learned a lot about her family’s medical history. “Not until I completed the study questionnaire did I fully realize how prevalent cancer is in my family,” she says. “I’m more predisposed to this disease than I originally thought and I’m a little embarrassed by my naiveté.”

That realization is exactly what Metcalfe wants others to take away from the study. “It doesn’t have to do with being Jewish. It doesn’t have to do with breast cancer,” she says. “Be aware of what’s happening with your relatives -- both on your mother’s side and your father’s side -- because it may inform what you are at a higher risk for.”

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