A new at-home saliva test could help identify men with a high risk of prostate cancer more accurately than blood tests, leading to earlier diagnosis and more successful treatment.
Prostate cancer is the second most common form of cancer among men, after skin cancer.
Currently, there is no standard test to screen for prostate cancer. A doctor may draw blood for a prostate-specific antigen test (PSA) or perform a rectal exam, but both of these types of screenings require follow-ups before a diagnosis can be made.
PSA blood tests measure the level of a specific molecule produced by the prostate. Yet diagnostic accuracy is compromised as an elevated PSA level can indicate a prostate issue but not necessarily prostate cancer.
In contrast, the new saliva tests analyze DNA, looking for a range of small genetic changes linked to prostate cancer.
Trials show this approach is more effective, and men who are categorized as high-risk because of these changes are more likely to have prostate cancer than men with elevated PSA levels.
Additionally, the spit test, which is not commercially available, falsely identified prostate cancer fewer times than the PSA test and detected a higher number of aggressive cancers that are fast-growing and more likely to spread.
“Right now, there’s no reliable method to detect aggressive prostate cancer, but this study brings us a step closer to finding the disease sooner in those people who need treatment,” said Naser Turabi, director of Evidence and Implementation Cancer Research UK.
“It’s encouraging to see that genetic testing might help to guide a more targeted approach to screening based on someone’s risk of developing prostate cancer. More research is now needed to confirm if this tool can save lives from the disease so that it can be rolled out to improve diagnosis.”
When the cancer is localized to the prostate, it is often curable. The five-year survival rate of prostate cancer, when it is detected early, is over 99%, according to the Prostate Cancer Foundation.
However, if prostate cancer spreads to other parts of the body, it can become deadly. When it metastasizes, prostate cancer commonly moves to the bones, lungs, lymph nodes, liver, or brain, making early detection critical.
In the study of 6,000 European men between 55 and 69, spit samples were collected to calculate polygenic risk scores (PRSs). These PRSs were based on 130 genetic variations associated with prostate cancer.
As with most types of cancer, certain groups are more at risk for prostate cancer. The average age of diagnosis is 67, and prostate cancer is considered rare in men who are under 40. African American men and Caribbean men of African ancestry are also more at risk for the disease.
Other risk factors for the disease include obesity, family history of cancer, plus factors like high blood pressure, lack of exercise, and being taller than average, according to the NIH.
In this latest study, men with the highest risk scores were referred for further screening.
Following an MRI and prostate biopsy, 40% were diagnosed with prostate cancer. Meanwhile, 78% of the men diagnosed as a result of the saliva test had a “normal” PSA level, a result that would typically indicate that no further screening is required.
Of the 187 cancers detected, 55% were aggressive cancers, compared with 36% of those identified by a PSA test in a recent study.
“With this test, it could be possible to turn the tide on prostate cancer,” said Ros Eeles, a professor at the Institute of Cancer Research and a consultant at the Royal Marsden NHS Foundation Trust, which jointly led the research.
”We have shown that a simple, cheap spit test to identify men at higher risk due to their genetic makeup is an effective tool to catch the cancer early.”
Treatment for prostate cancer includes several options, depending on the specific diagnosis. Patients may undergo surgery, chemotherapy, immunotherapy, radiation, or targeted drug therapy.
In addition to the early detection and treatment of prostate cancer, researchers are hopeful the saliva test will eliminate unnecessary medical intervention in low-risk patients.
PSA tests do not differentiate between aggressive or non-aggressive tumors, leading many men to be diagnosed with cancers that would not hurt them in the long run and/or being referred for unnecessary MRI scans, invasive biopsies, and other treatments.
“Building on decades of research into the genetic markers of prostate cancer, our study shows that the theory does work in practice — we can identify men at risk of aggressive cancers who need further tests and spare the men who are at lower risk from unnecessary treatments,” said Eeles.
