An at-home spit test is better at identifying prostate cancer risks in some men than the standard test on the market, a new study has found.
The findings mean those at higher risk of prostate cancer – one of the most common forms of cancer among men – could someday have a new screening option that is less likely to return false-positives that require burdensome follow-up.
For the study, which was published in the New England Journal of Medicine, researchers took saliva samples from about 6,400 men in their 50s and 60s in the United Kingdom, and used DNA samples to calculate their prostate cancer risk, which is called a polygenic risk score.
They then did additional scans and biopsies for men with the highest risk scores, and diagnosed 40 per cent of them with prostate cancer.
Among men flagged as high-risk through the standard prostate screening tool, 25 per cent actually have cancer – significantly worse than the spit test.
That means introducing the spit test could “identify men at risk of aggressive cancers who need further tests and spare the men who are at lower risk from unnecessary treatments,” said Rosalind Eeles, one of the study’s authors and a professor of oncogenetics at the Institute of Cancer Research (ICR).
False positives of standard tests
The standard tool is a blood test that tracks a protein called prostate-specific antigen (PSA). Elevated PSA levels can be a sign of prostate cancer.
The PSA test is typically used for men at higher risk of cancer due to their age or ethnicity, or because they have symptoms. Men with high PSA levels are sent for additional tests to confirm whether they have cancer.
But it has a tendency to give false positives and detect low-grade cancers that are unlikely to ever be life-threatening, meaning many men undergo unnecessary scans, biopsies, and treatments, according to the ICR.
The researchers said the saliva test could serve as another screening tool offered to men who are either at higher risk of prostate cancer or are showing symptoms.
Future studies will track men with high polygenic risk scores to see whether they go on to develop prostate cancer.
But it could be years before the spit tests become standard practice due to the logistics and cost of integrating them into the healthcare system, according to Michael Inouye, a professor of systems genomics and population health at the University of Cambridge who was not involved with the study.
“To me, the study really makes me start to believe that these investments are worth it,” he said.
