Genetic scientists have made a major leap forward in being able to identify people who are at most risk of developing three of the leading cancers.
They say it will lead to improved screening for breast, prostate and ovarian cancers.
The research should also lead to a simple and cheap DNA “spit test” in a GP surgery which will reveal more accurately a patient’s lifetime risk of developing one of the cancers.
In a few years’ patients will be able to use the “spit test” results to plan their individual treatment and screening regime with their GPs.
A huge four year international study – the largest ever of its kind - has found another 80 genetic areas that can increase a person’s inherited risk of breast, prostate and ovarian cancers – doubling to 160 identified common gene faults in cancer patients.
More than 4,000 scientists studied the DNA of over 200,000 people – half with cancer and half without – to find the genetic variations. called single nucleotide polymorphisms (SNPs) – linked to an increased risk of developing cancer.
The researchers led by the University of Cambridge and Institute of Cancer Research, London, say that for the one in 100 people who have lots of the new cancer genetic changes could see their risk of developing prostate cancer rise by nearly 50 per cent and breast cancer by 30 per cent
In Ovarian cancer 11 new gene variations were found – not enough to raise the risk significantly.
Dr Harpal Kumar, chief executive of charity Cancer Research UK, which backed the project, said: “We have known for some considerable time that some proportion of cancers are people who have an increased risk from birth – and we know that because cancers are congregated in some families.
“Over the years we have found many of the faults in genes which can raise someone’s risk of getting cancer.
“By searching for variations in cancer patients’ DNA we are able to piece together pictures of gene variations which are able to increase the risk of someone getting cancer.
“The idea here is to be able to predict on an individual person’s level what is their risk because that can help us underpin more personal prevention and screening in the future
“It can also help us identify what is driving different types of cancer to enable us to develop different therapeutic advances for those different types.”
Around 60% of the genetic risks of developing the three cancers is still unexplained. Lifestyle factors like obesity and smoking also play their part.
The researchers found that five per cent of women with the BRCA1 fault who carry most of the genetic variants linked to BRCA1 have over an 80 per cent chance of developing breast cancer by the age of 80. Women with few of these variants and a BRCA1 fault have a 50 per cent risk of developing the disease.
The scientists also found gene changes only linked to the most aggressive form of breast cancer called oestrogen receptor negative – suggesting it develops in a unique way, which could open the door to new treatments.
Professor Ros Eeles. Professor of Oncogenetics at Cambridge University, said: “From basic science you can get clues how to treat patients.
“A lot of these variants are in part of the genome which control how genes are switched on and off. That gives an important clue how we might develop new drugs.”
In prostate cancer having the newly discovered genetic markers would increase your risk of developing the cancer from the average one in ten to one in two.
“It’s a bit like a card game each person individually will have their own risk depending on these markers “ she said.
The researchers say knowing more about the DNA of inherited cancer will also enable them to screen out those at low risk.
And a patient’s cancer DNA should be available through a simple £5 test in the GP surgery.
Professor Eeles added: “You can do it by spitting into a tube. It is much cheaper than a mammogram. These kind of test results can be read by a computer.
“Eventually, it will be at point of care. The person making the decision will be your GP.
“We are not there yet but I really think we are going to get there fast.”