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My relative has cancer, should I worry? Encouraging cascade genetic testing

Online outreach and low-cost testing can encourage relatives of cancer patients to assess their own cancer risk through 'cascade' testing.

When a loved one has cancer, many of us turn to thoughts of comfort and help. (I'm Scandinavian by background, so I immediately warm up my formidable arsenal of casserole recipes.) But when the loved one is also a close relative, we also wonder whether there's a genetic link that could affect others in the family, including ourselves.

Fortunately, most cases of cancer are sporadic, meaning there's no obvious genetic cause. But some do arise as the result of specific, heritable changes in key genes. In those cases, a carrier's first-degree relative has about a 50 percent chance of harboring the same mutation.

Allison Kurian, MD, a Stanford breast and gynecologic cancer specialist, and Jennifer Caswell-Jin, MD, an instructor of medicine, together with researchers at the Bay Area company Color, which provides genetic testing, recently explored ways to encourage the first-degree relatives of people carrying cancer-associated mutations to be tested themselves.

Their finding? Online outreach coupled with low-cost testing reaches more people than traditional efforts.

They reported their research this week in the Journal of the National Cancer Institute.

From our release:

Increasingly, newly diagnosed cancer patients are turning to genetic testing in a quest to understand why they’ve developed the disease. The discovery of a disease-associated mutation can help drive treatment decisions and provide clues as to the cancer’s origin. But there’s another important, often overlooked, benefit: The test results can help a patient’s healthy first-degree relatives assess their own genetic risk for cancer...

However, this kind of cascade testing, in which a positive result in a cancer patient triggers waves of genetic testing among the patient’s relatives, remains relatively rare — in part because physicians are often prohibited from directly contacting a patient’s relatives, and people reeling from their own recent diagnosis may not immediately consider the health implications for their loved ones. Testing can also be expensive and is not always covered by insurance.

The researchers enrolled nearly 1,000 people who either carried any one of 30 known cancer-associated mutations or who were first-degree (think mother, father, siblings and children) relatives of the carrier. Participants were encouraged to invite additional first-degree relatives to undergo genetic testing for an out-of-pocket cost of $50, about one-tenth the normal cost. Those who themselves tested positive could then invite additional first-degree relatives to participate in the program.

Identifying healthy people who carry a cancer-associated mutation could confer a significant public health benefit.

As I explained in our release:

Although not everyone with a cancer-associated mutation will go on to develop the disease, the knowledge that one is a carrier can help people and their doctors make informed health care decisions while they are still healthy. For example, women with BRCA1 or BRCA2 mutations who have a vastly increased risk of developing breast or ovarian cancers may choose to undergo prophylactic mastectomies or have their ovaries removed. Other types of mutations, such as those that increase one’s risk of colon cancer, may indicate the need for increased or more frequent screening.

The possibilities are exciting, Caswell-Jin said. "We expect the proportion of people undergoing genetic testing for disease-associated mutations will continue to increase. We need to make sure they get the support they need to understand their results, and to encourage additional support and follow-up."

Photo by Goultard

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