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Understanding BRCA 1, BRCA 2 Genetic Tests

By BONNIE PRESCOTT, Beth Israel Deaconess Medical Center Correspondent

If you've seen any news reports in recent months, you're probably aware that a lot of discussion has focused on BRCA 1 and BRCA 2 genes. Mutations in these two genes are responsible for about five percent of all cases of breast cancer and approximately 20 to 25 percent of all hereditary breast cancers. The genetic mutations also account for approximately 15 percent of cases of ovarian cancer.

DNA Structure
Long structure of the DNA double helix in depth of view. (Credit: IStockPhoto)

One of the reasons for the news coverage revolved around Angelina Jolie's decision to undergo removal of her ovaries to reduce the risk of developing ovarian cancer, as she carries the BRCA 1 mutation.

Jolie had previously undergone mastectomies of both breasts to sharply reduce the risk of developing BRCA1-related breast cancer.

At nearly the same time came reports of a new, inexpensive test kit for the BRCA genes, which is expected to reduce the cost of a genetic test from thousands of dollars to $249. The new test, would also assess 17 other cancer-risk genes.

Which raises the questions: Who exactly should be tested for these gene mutations and what can the tests be expected to reveal?

Family History

The decision to undergo BRCA testing is based on a woman's family history, explains Dr. Nadine Tung, director and founder of the Breast Cancer Genetic Risk Evaluation Program at Beth Israel Deaconess Medical Center (BIDMC).

"BRCA 1 and BRCA 2 are genes that produce tumor suppressor proteins, which mean that they help repair damaged DNA and make sure that a cell's genetic material is stable," explains Tung. "We all have the BRCA 1 and BRCA 2 genes and, hopefully, they're working normally."

However, when either of the genes becomes mutated or damaged, cells are more likely to undergo alterations that can lead to cancer. In 1997, BRCA 1 and BRCA 2 were identified as the first two genes for which an inherited genetic abnormality predisposed women to both breast cancer and ovarian cancer.

"The purpose of genetic testing is to identify those women and men who are at markedly increased risk of breast, ovarian and other cancers so that steps to reduce or eliminate that risk can be taken," adds Dr. Tung. "This can be achieved through intensive screening, medication or preventive surgery."

Pre-Test Counseling

The test itself consists of a simple blood test. But the implications that can emerge from the tests and what they reveal are often anything but simple. This is why BIDMC's Breast Cancer Genetic Risk Evaluation Program includes careful pre-test counseling to help patients understand the sometimes complex ramifications of these genetic tests.

"It's complicated if the results come back positive," says Dr. Tung. "The cancer risks associated with mutations in some genes other than BRCA 1 and BRCA 2 are not yet known. In addition, mutations in other genes may confer high risks of cancers, although the benefit of screening or preventive surgery is unknown. And sometimes, changes are found in a gene and it isn't clear if that 'variant' is benign or worrisome. This can be stressful for patients."

She adds that it can be equally as complicated if the results come back negative, but there is a strong family history of cancer. "Should someone be reassured by a negative genetic test? Issues such as these can lead to a lot of stress and anxiety -- not just for the individual, but for the whole family."

Which is why, Dr. Tung says, she is concerned about the new inexpensive test kits that are coming on the market.

"I think it's critical that patients undergo pre-test counseling before taking any genetic tests," she explains. "Genetic counselors are equipped to not only provide patients with medical facts, but also help them to understand the many other issues that can emerge when you decide to find out if you carry a BRCA or other mutation."

At BIDMC, pre-test counseling begins with a 90-minute informational session.

"We first review the patient's own medical history and the family medical history," says BIDMC Genetic Counselor Jill Krejdovsky. "That information allows us to do a risk assessment – how likely is it that the cancer is inherited? Then we discuss the pros and cons of undergoing genetic testing. We discuss what recommendations might be made if the test comes back positive, the emotional impact this might have and the implications for other members of the family."

Because patients may feel anxious about cancer running in their families and feel guilty at the thought of passing the gene on to their own children, counselors are equipped to help allay these concerns and also to recognize when a social worker should join the conversation if needed.

"Genetic tests can help guide patients in critically important decisions," adds Dr. Tung. "But pre-test counseling, whether face-to-face with a counselor, or by teleconference is key to preparing patients for these tests and helping them to understand a complex and difficult issue."

Above content provided by Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.

Posted May 2015

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