A clinical study found an at-home test based on the DNA found in spit samples could detect cases of prostate cancer that would otherwise slip past a standard blood draw.
Researchers at The Institute of Cancer Research (ICR) in London and The Royal Marsden NHS Foundation Trust discovered a saliva test could help spot the signs of hidden tumors in people whose prostate-specific antigen (PSA) levels fell within normal ranges among men with an already increased genetic risk for the disease.
They also found that when cases were identified, they included a higher proportion of aggressive malignancies versus a PSA blood test. The results of the trial—dubbed BARCODE 1, which studied more than 6,100 men in Europe—were presented at the annual meeting of the American Society of Clinical Oncology in Chicago.
In the U.S., PSA tests are currently not highly recommended as a screening option. False-positive readings—which the study’s researchers pegged at potentially as high as three out of every four results—and alerts to benign growths could lead patients to undergo a series of avoidable biopsies, MRI scans or other diagnostic procedures. The researchers said a saliva-based test could offer an additional tool.
“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,” Ros Eeles, Ph.D., a professor of oncogenetics at ICR, said in a statement.
The study’s test delivers a personalized polygenic risk score based on 130 mutations linked to prostate cancer. The researchers took the people with the highest 10% of scores and offered further screening, including MRI and prostate biopsies.
Out of those 558 men, 187 were diagnosed with cancer—about 78% of whom had PSA levels considered normal and may not have been referred for additional testing.
At the same time, about 55% were classified as aggressive cancers, compared to the 35% identified by a PSA test in a recent study, according to researchers. In addition, the saliva test detected many cancers confirmed by tissue biopsy that were not seen on an MRI scan.
“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,” Eeles said. “Our next step will be for us to test the genetic markers we have identified that are associated with a risk of prostate cancer in diverse populations, to ensure this test can benefit all men.”
The researchers said 62 of the 187 cancers needed further treatments, while the rest were actively monitored.
“Cancers that are picked up early are much more likely to be curable, and with prostate cancer cases set to double by 2040, we must have a programme in place to diagnose the disease early,” said Kristian Helin, Ph.D., chief executive of the ICR.
“We know that the current PSA test can cause men to go through unnecessary treatments and, more worryingly, it’s missing men who do have cancer. We urgently need an improved test to screen for the disease,” Helin said. “This research is a promising step towards that goal, and it highlights the role that genetic testing can play in saving lives.”
The study was funded in part by the European Research Council, the Bob Willis Fund, Cancer Research UK and the Peacock Trust.