It might seem inconceivable that a simple saliva test can tell you your chances of developing cancer.
But evidently it can. And the reason is crude but simple: Your genetic makeup can be found in your spit.
Scientists are now able to extract DNA from cells — mostly leukocytes, also known as white blood cells — that are floating in your saliva.
This has already been demonstrated globally in popular genealogical tests from such companies as Ancestry.com and 23andMe, which can literally tell us where, and who, we came from.
Now, a relatively simple 10-minute saliva-based DNA test can also identify variations on genes that identify men who are at the highest risk of developing prostate cancer.
The test can also tell us about the risk of other cancers as well.
To that end, a group of scientists from the Institute of Cancer Research (ICR) in London have initiated a clinical trial of a saliva-based DNA test to identify with greater clarity men at the greatest risk of developing prostate cancer.
Other than skin cancer, prostate cancer is the most common cancer in American men, according to the American Cancer Society.
And prostate cancer is the most frequently diagnosed cancer among men in Europe, according to the Joint Research Centre (JRC), the science and knowledge service of the European Commission (EU).
The ICR trial follows up on the findings of a published in the journal Nature Genetics of more than 140,000 men that identified 63 new genetic variations in the DNA code that increase the risk of prostate cancer.
“The British study broke new ground in prostate cancer research,” Dr. Jonathan Simons, chief executive officer of the Prostate Cancer Foundation (PCF), the largest nonprofit prostate cancer organization in the world, told Healthline.
“But there is much more to learn about younger men who present with more aggressive earlier cancers,” said Simons, a medical oncologist and internationally recognized leader in prostate cancer research.
Dr. Iain Frame, director of research at Prostate Cancer UK, said in a statement, “This new research could help men to understand their individual genetic risk of prostate cancer, which could prompt them to speak to their GP about the disease.”
Saliva tests already on the market
Saliva tests for prostate cancer patients are a significant development in what has been dubbed precision medicine, which simply means the customization of treatments for individual patients based on their genetic makeup.
Several saliva-based DNA tests have already been approved in the United States by the Food and Drug Administration (FDA).
They still must be ordered by a physician.
When Simons decided to test himself for a possible predisposition to prostate cancer, he chose the saliva test that he got through the mail.
“I wanted to understand the patient experience as it relates to saliva testing for genetic risk for prostate cancer. I ordered a test with a credit card and took it myself,” he said.
The test is straightforward. The instructions are simple. Just spit into the plastic tube provided, seal it up, and send it back.
After a period of a few weeks, you will receive a report that tells you whether or not any genetic mutations were identified.
The test in which Simons participated, which looked at 31 genes, showed no mutations. Which means he does not fall into the high-risk group.
“I learned from this saliva test that my lifetime prostate cancer risk is the same as the general population, and the risk of prostate cancer for my sons is the same,” he said.
Simons said the test report also gave him the option of contacting a genetic counselor.
If someone has the mutant gene markers, he said, the patient is then walked through what the results mean, first by a urologist, and then by a genetic counselor.
A genetic counselor is someone with genetic training who explains to the patient what was found on the test and what the implications are for the patient and the family in terms of disease risk.
“The genetic counselor is there to answer any questions the patient has and give [the] patient a life plan,” Simons said.
Test may help prevent cancer
The saliva test is getting an ever-increasing amount of attention among leading cancer researchers and clinicians nationwide and worldwide.
Dr. Heather Cheng, director of the Prostate Cancer Genetics Clinic at the Seattle Cancer Care Alliance, is conducting an ambitious clinical trial of the saliva test in Washington State.
“Saliva testing for better understanding of inherited risk for cancer is another good option along with blood testing, and may help men learn vitally important information that can be helpful for medical decision-making with their doctors,” said Cheng, who’s also an assistant professor at the University of Washington School of Medicine and an assistant member of the Fred Hutchinson Cancer Research Center.
“This may be especially true for men with advanced prostate cancer that has spread outside the prostate,” she said.
Cheng said it is “critically important” for people to understand that there are different types of saliva tests available.
Some, such as Ancestry.com and 23andme, are recreational and not intended for healthcare, while others are certified medical tests.
“When a person is seeking medical-grade information, he or she should have a conversation with their doctor and/or a genetic counselor to get the best understanding of the risks and benefits before doing the test,” Cheng explained.
The fact that these tests are becoming more accessible to the public and are giving us a better idea of our genetic makeup and our risk for cancer is a significant breakthrough for patients.
In addition, because researchers now know that some men with prostate cancer have these genetic mutations and are gaining more specific knowledge about this topic, new treatments that harness the body’s own immune system are being developed to treat prostate and other cancers.
Harnessing the body’s immune system is bringing long-term remissions and even cures in several types of cancer, including Hodgkin’s and non-Hodgkin’s lymphoma, melanoma, and lung cancer.
While immunotherapy has not yet been optimized in prostate cancer, things are moving in that direction.
Last year, the FDA approved the immune checkpoint inhibitor Keytruda from Merck for treatment of all solid tumors with so-called MMR mutations or MSI, including prostate cancer.
The more researchers learn about our genetics, the more specific, and effective, these treatments will be.
Ros Eeles, PhD, professor of oncogenetics at the ICR, said in a press release, “If we can tell from testing DNA how likely it is that a man will develop prostate cancer, the next step is to see if we can use that information to help prevent the disease.”
New subtype of prostate cancer
A Prostate Cancer Foundation-funded study published this month in the scientific journal Cellhas identified a new subtype of advanced prostate cancer that occurs in about 7 percent of patients in advanced stages of the disease.
The subtype is characterized by loss of the gene CDK12. It was found to be more common in metastatic prostate cancer compared with early stage tumors that had not spread.
Tumors in which CDK12 was inactivated were responsive to immune checkpoint inhibitors, which are a type of immunotherapy treatment that to date has had only limited success in prostate cancer.
“Because prostate cancer is so common, 7 percent is a significant number. The fact that immune checkpoint inhibitors may be effective against this subtype of prostate cancer makes it even more significant,” Dr. Arul Chinnaiyan, a senior study author and director of the Michigan Center for Translational Pathology, said in a statement.
“This is an exciting prospect for patients who have CDK12 alterations and may benefit from immunotherapy,” he added.
Howard Soule, PhD, executive vice president and chief science officer of the Prostate Cancer Foundation, said in a statement, “This very promising study suggests that CDK12 loss may be a biomarker for identifying prostate cancer patients who may respond to checkpoint immunotherapy.”
He added, “The Prostate Cancer Foundation is proud to have funded this team, which continues to make foundational strides in identifying actionable genomic mutations in prostate cancer and using this information to identify new classes of precision treatments that can be used to improve the lives of men with prostate cancer.”
Simons told Healthline that if there is a mutation in the CDK12 gene, and the patient’s cancer had a mutation in the second copy in the tumor, “this confers a very high probability of a complete remission with immunotherapy.”
Simons predicted that within five years, “Every urologist will have an app for this and will be working with patients and getting a genetic counselor involved. Genes don’t have to be destiny.”
Also in the very near future, he said, “Saliva tests will become an essential companion to the PSA test. The PSA test is important, as well, and gives us information that the saliva test does not. But soon both tests will be essential.”