A saliva test to reveal a patient’s risk of breast or prostate cancer could be available in doctors’ surgeries within five years, according to a “groundbreaking” study.
A major research drive involving more than 1,000 experts has revealed more than 80 genes which help determine from birth whether or not someone will develop cancer during their life.
Screening patients for genetic variants linked to cancer could help doctors predict more accurately whether they are at high risk of the disease, and in some cases begin treatment to prevent it ever developing.
For example, the tests could identify the one in 100 men whose genes give them a 50 per cent chance of developing prostate cancer, and the one in 100 women whose likelihood of developing breast cancer is 30 per cent.
The tests could be carried out by family doctors, would be cheaper than current breast screening methods and could also identify patients at low risk of cancer who could potentially be spared additional, more invasive tests.
Dr Harpal Kumar, chief executive of Cancer Research UK, said the research project, which resulted in 12 academic papers published across five journals, could even lead to new treatments.
Although about 60 per cent of the genetic risk factors for all three cancer types remain unexplained, the findings are a significant step forward in our understanding of the inherited causes of the condition.
In the case of prostate cancer 18 of the 23 variants applied specifically to the most aggressive types of the disease.
Prof Ros Eeles of the Institute of Cancer Research said: “These results are the single biggest leap forward in finding the genetic causes of prostate cancer yet made. They allow us, for the first time, to identify men who have a very high risk of developing prostate cancer.
“If we can show from further studies that such men benefit from regular screening, we could have a big impact on the number of people dying from the disease.”
Although the variants, known as single nucleotide polymorphisms (SNPs), make little difference on their own, when added together they can greatly raise the risk of the disease.
In prostate cancer, for example, the one per cent of men with the highest number of the SNPs are 4.7 times more likely to develop the condition compared with the average man.
Women in the top percentile for breast cancer variants have a 30 per cent chance of developing the disease – excluding those who carry the BRCA1 and BRCA2 genes which are already known to cause extremely high risk of the disease.
Researchers now hope to develop tests which could analyse patients’ saliva for SNPs linked to particular cancer types, and which could be performed and analysed by GPs.
Prof Eeles said such a test could be widely available within five years, while a version of the test could be available to women already known to be at high risk of breast cancer within 18 months.
Prof Doug Easton, another of the study leaders, added: “We are on the verge of being able to use our knowledge of these genetic variants to develop tests that could complement breast cancer screening and take us a step closer to having an effective prostate cancer screening programme.”