Genetics-based medicine a matter of debate

Scientists debate value of genetics-driven medicine while patients live with ambiguity.

By Kathleen McLaughlin / The Bulletin

Published May 9, 2016 at 12:11AM / Updated May 9, 2016 at 06:42AM

Across the top of the page of breast cancer patient Marta Izo’s genetic test results is a big red stripe.

Positive, high risk for breast cancer.

Izo, 65, carries a variation in the ATM gene that’s associated with a high risk of breast cancer and an elevated risk of pancreatic cancer, according to testing company Myriad. Less than 1 percent of the population carries this variation of the ATM gene, which plays a central role in cell division and flagging damaged DNA.

The ATM gene was suspected as a cancer link because it’s the key player in an autosomal recessive disease, ataxia telangiectasia, or Louis-Bar syndrome, which occurs in extremely rare cases when someone inherits two copies of the mutated gene. Families in which Louis-Bar occurred also seemed to have higher instances of breast cancer.

Now research on people who carry a single copy of the ATM mutation indicates women have a 17 to 52 percent chance of developing breast cancer from age 50 to 80, compared with 10.2 percent of all women in that age range.

The risk of pancreatic cancer, which applies to women and men, isn’t quantified.

When Izo was diagnosed in 2014, her oncologist at Bend Memorial Clinic didn’t think she was a carrier of the BRCA1 or BRCA2 gene mutations, well-known because they mean a high risk of breast cancer, but based on her family history, some other genetic syndrome might play a role in her cancer, Izo said. Myriad was to begin offering a 25-gene panel test that summer, so she took it, even though she’d already undergone a lumpectomy and radiation.

“I think it’s kind of a blessing and a curse,” said Izo, a nurse at St. Charles Bend.

Because of her breast cancer risk, Myriad recommends clinical breast exams every six to 12 months and an annual MRI in addition to mammography.

“They will watch me differently and they will treat me differently, but it will always hang over your head a little bit that you have this gene mutation,” Izo said.

This type of genetic testing is the bread and butter of precision medicine, which aims to develop treatments tailored to individual patients. The National Institutes of Health this year made its first grants under a $200 million initiative, which seeks to build large-scale participation in research. The effort depends on people like Izo, who authorized her test results to be included in a national registry of people who’ve had this newer form of genetic testing, called multiplex gene panels.

With the panel tests, doctors no longer have to guess which gene to test, and they’re learning more about common genetic links across cancer types. Variations in the BRCA1 and BRCA2 genes are also associated with ovarian, pancreatic, melanoma and prostate cancer.

In another example, mutations in one of five genes can cause Lynch syndrome, which is behind 3 to 5 percent of colorectal cancers. People with this syndrome have cancer at a young age and may experience multiple types of cancer over their lifetime.



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