Newer tests clarify hereditary risk of cancer

By | September 18, 2014

“There is this group of people who think they don’t need to worry about getting cancer and believe they don’t have a high family risk of getting cancer, but unfortunately do,” said Mahon, a professor in internal medicine at Saint Louis University.

Mahon says her requests for genetic testing for breast cancer have more than tripled since 2013, when actress Angelina Jolie announced she had a double mastectomy because she was at genetic risk of developing breast cancer.

Older genetic screenings were for the BRCA 1 and 2 genes, which are linked to the development of breast, ovarian, prostate, melanoma, pancreatic and other cancers.

However a new generation of genetic tests can detect as many as 25 other, less common genes that show a familial predisposition to cancer.

“It’s important for people to understand what genetic test they were given and how complete they were,” Mahon said.

“Many people have tested negative for BRCA 1 or 2 and mistakenly think they do not have an increased hereditary risk for developing cancer. It is possible that newer testing, through next generation platforms, could identify a less common susceptibility gene and clarify their risk.”

For those who had early, less complete genetic tests, catch up panels are available to screen for other genes that raise their risk of developing cancer. “Most of these genes are associated with multiple cancers,” Mahon said.

Those who could be at genetic risk of developing cancer include people who have:

• Several close relatives on the same side of the family who have cancer

• Cancer at a much younger age than average, for instance, before age 50 for breast or colon cancer

• A close relative who has more than one type of cancer

• A close relative who has cancer in both paired organs, such as in both breasts

• Cancer occurring in more than one generation

• Several rare cancers in a family

• Ancestors of Ashkenazi Jewish descent

While knowing you are at a higher genetic risk for cancer is stressful, that knowledge can guide how you manage your health going forward. For instance, you might be more likely to stay on top of health screenings or choose to have preventative surgery, which can be a difficult choice.

“For instance, a person who has a higher risk of developing colon cancer might have a colonoscopy at a younger age to detect potential cancer at an earlier and more treatable stage,” Mahon said. “Someone who is at risk of melanoma needs to be particularly vigilant and make sure they’re seen by a dermatologist for annual skin checks.”

Testing negative for a known family mutation doesn’t necessarily mean a person won’t get cancer, Mahon added. While that person is not genetically predisposed to cancer, and won’t pass along that risk to his or her children, he or she has the same risk for developing cancer as those in the general population.

Deciding whether or not to have genetic testing to see if you are at hereditary risk for cancer is both courageous and complicated, and a credentialed genetics professional can help guide you in your decision, Mahon said.

Once the test is completed, interpreting results can be challenging and best done by a credentialed genetics professional, she added.

“Genetics professionals serve entire families, not just individuals,” Mahon said. “When testing is coordinated by a genetics professional, all at-risk members are identified so they can choose to be tested.”

Saint Louis University Cancer Center combines compassionate and individualized care with the latest advances in research, prevention and education. To schedule an appointment with a Cancer Center specialist, call (314) 977-4440 or (866) 977-4440.

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