Know the score on a new type of DNA testing: Polygenic risk scores (PRS)
Catch this AnCan webinar on July 31 featuring DNA guru Dr. Todd Morgan
By Howard Wolinsky
Genetic testing is a three-legged stool.
Most of us have only heard of two of the legs (germline and somatic), but we (and our urologists and GPs) have heard little to nothing about the third leg--polygenic risk scores (PRS), which are just becoming available.
Dr. Todd Morgan, chief of urological oncology at the University of Michigan (Go Blue!), a leading prostate cancer genetics researcher, will school us on the role of DNA in prostate cancer--including PRS--in a webinar for AnCan on July 31 at 8 p.m. Eastern.
To register for the program, entitled “How and why PCa genomic tests work ... What's Inside the Black Box?", go to: https://tinyurl.com/ancanpcagenwebinar If you can’t make it, just sign up and we’ll send you the link.
Genetics, like nutrition, gets short shrift in the public schools as well as medical schools. And unless you are a molecular biologist or the like, you probably don’t know much either.
You may have undergone a spit germline or DNA test of inherited genes that can reveal whether we have mutations such as BRCA 2. If you look like a perfect Gleason 6, germline testing could indicate you inherited a gene associated with more aggressive cancers requiring being monitored more closely or even needing to undergo aggressive treatment.
(BTW, you can get a free germline spit test from the Promise study at https://www.prostatecancerpromise.org/how-it-works/)
Then there’s somatic or genomic testing, where genetic sequencing is performed on your cancer samples or cores. These tests, under the Decipher, Prolaris and Oncotype DX, brand names, can provide guidance on whether you are a candidate for Active Surveillance or active treatment.
Germline testing looks at single markers, known as SNPs, short for single-nucleotide polymorphisms, found in patients with prostate cancer that are not found in populations of men who don’t have prostate cancer. Call these monogenic marker tests.
Polygenic, as implied in its name “poly” from the Greek for “many,” not Polly, your parrot, looks at multiple markers associated with a condition. Hundreds, maybe even hundreds of thousands of SNPs or polygenic markers.
PRS is also being developed for prostate cancer and other common diseases like heart attacks, breast cancer, Alzheimer’s and diabetes. Gerline tests focus on rare mutations.
The genes interact with each other and can have a powerful impact on common diseases even if doctors don’t completely understand how this happens.
In Prostate Cancerland, PSR could be a tool, along with PSA testing, somatic and germline testing, MRIs and biopsies in helping us.
They’re all pieces of the puzzle.
PSR can predict the likelihood that the tested may develop prostate cancer. Keep in mind, it can’t yet predict how aggressive the cancer will be.
In prostate studies, typically, they now use 250 to 500 or so markers to be weighed in a mathematical model and used as an algorithm to predict risks.
In research for another article, I spoke with Giordano Botta, PhD, a molecular biologist and CEO of one of the testing companies that sells a PSR for prostate cancer and other diseases. Allelica calls itself “The Polygenic Risk Score Company.” For more on this test, go to https://allelica.com/prs-test/page-3.html
Advocates for this testing say a one-time PSR someday potentially may spare men from undergoing PSA (prostate-specific antigen) blood level testing, the doorway to Active Surveillance and active treatment.
Not everyone is that enthusiastic. But the optimism in some quarters is intoxicating to me, someone who has been on the low-risk cancer treadmill for 13 years.
Dissemination of PRS is expected over the next five years or so.
Let me stress: I am not recommending that you go out and get tested. I will give it a whirl and see what I find out. Watch this space.
(I have been a guinea pig for genetic tests over the past 20 years, originally for family history.
(I tracked my family to Medieval Spain —the Royal Astronomer to Ferdinand and Isabella was in my line—and to ancient Palestine—where I had both Hebrew and Canaanite roots. I can even tell you in which migration wave my ancestors were in departing Africa tens of thousands of years ago.)
I am just hoping to inform you about a technology that is emerging, that you’ll be hearing a lot more about in the years ahead. A better-informed patient/consumer makes better choices working with their doctor and family.
There are other PRS players out there, like Genomics PLC. Myriad Genetics, well known for its Prolaris and BRCA tests, has a PSR for breast cancer known as MyRisk Hereditary Cancer test.
One of the big shortcomings of PSR scores is that generally they are focused on patients of European ancestry. But d efforts are underway to develop risk scores for Blacks, Asians, and other populations.
Morgan sees promise in PSR. but feels there needs to be patient education and physician education.
Join the process at the webinar on July 31. Register at https://tinyurl.com/ancanpcagenwebinar
If you have some questions for Dr. Morgan, write to Joe Gallo at joeg@AnCan.org