Scientists have developed a saliva test that could “change the tide” on prostate cancer around the world by detecting the disease early, identifying which parts of men are at high risk and sparing other patients unnecessary treatment.
The number of men diagnosed with prostate cancer worldwide is predicted to double to 2.9 million per year by 2040, with annual deaths expected to increase by 85%. Prostate cancer is already the most common male cancer in more than 100 countries.
Early diagnosis is crucial, but experts say the current standard PSA blood test could miss some men who actually have cancer, and cause others to undergo unnecessary treatment or pointless further tests and scans.
Now researchers from the Institute of Cancer Research, London (ICR) and the Royal Marsden NHS Foundation Trust seem to have found a better alternative.
A new saliva test that collects a DNA sample in seconds is more accurate than the current standard blood test, according to a study being presented this weekend at the world’s largest cancer conference.
“This test could help change the tide of prostate cancer,” said Ross Eales, professor of tumour genetics at ICR. “We have demonstrated that a simple, inexpensive saliva test that identifies men at high risk because of their genetic makeup is an effective means of detecting the cancer early.”
Speaking at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago, Eales said the groundbreaking discovery came after decades of research into genetic markers of the disease.
“Our study shows that the theory actually works – we can identify men at risk of aggressive cancers who require further testing and spare men at low risk from unnecessary treatment.”
After studying the DNA of hundreds of thousands of men, scientists and doctors developed the saliva test, which works by looking for genetic signals in saliva that are linked to prostate cancer.
In the Barcode-1 trial, researchers recruited more than 6,000 European men to pilot the saliva test, all of whom were recruited from general practices and were aged between 55 and 69 years, an age at increased risk of prostate cancer.
Once the saliva was collected, the test calculated each man’s polygenic risk score (PRS), which was based on 130 genetic variants in his DNA code that are associated with prostate cancer.
According to the ICR, for people at highest genetic risk, the test had fewer false positives than PSA, detected cancer cases missed by PSA alone, and had a higher rate of aggressive cancers than PSA testing.
The test was also able to accurately identify men with prostate cancer that would have been missed by MRI scans.
Diresh Turnbull, 71, from Brighton, was one of the first men in the world to try the saliva test and received the results which revealed he had prostate cancer.
He said: “It was a real shock when I was diagnosed as I had no symptoms whatsoever, so I don’t think I would have been diagnosed at this stage if I hadn’t been on the trial.”
Prime Minister Turnbull underwent robotic surgery to remove part of his prostate and is progressing well.
He said: “Because the saliva test showed that I was at high genetic risk of developing the disease, my younger brother, who was too young to take part directly in the study, also enrolled and was found to have a malignant prostate tumour. It’s incredible to think that this research has saved two lives in our family.”
Mr Eales, a consultant in clinical oncology and cancer genetics at the Royal Marsden NHS Foundation Trust, warned that more research was needed before the test could be widely introduced.
“Our next step is to test for the genetic markers that we have identified as associated with prostate cancer risk in different populations to ensure that this test can benefit all men.”
Ageing populations and rising life expectancies are resulting in an increasing number of older men living longer around the world. Because the main risk factors for prostate cancer — being over 50 years old and having a family history — are unavoidable, experts believe that lifestyle changes and public health interventions alone will not be enough to prevent a sharp rise in cases.
But better testing and earlier diagnosis could help reduce the burden and save lives.
“Cancer is much more likely to be cured if it is detected early,” said ICR chief executive Professor Christian Helin. “With prostate cancer cases expected to double by 2040, we need to put in place programmes to diagnose the disease earlier.”
“We know that current PSA tests may cause men to undergo unnecessary treatment and, even more concerning, may miss men who have cancer. Improved tests to screen for this disease are urgently needed. This study is a promising step towards that goal and highlights the role genetic testing can play in saving lives.”
