So the question many researchers are asking is whether it’s possible to unpick this complex web of influences and accurately predict a person’s cancer risk.
Currently the answer to this challenging question is ‘no’ – at least for most of us. But – never ones to be daunted by a challenge – some researchers are trying to combine our ever-growing knowledge of the genetic differences between individuals, with a person’s age and life history, to try to predict their cancer risk.
Their goal is to identify people with a high risk of cancer, and to offer them tailored screening, monitoring or lifestyle advice.
Dr Antonis Antoniou, at the University of Cambridge, is one of these researchers. A trained statistician, he is currently developing computer programmes to help doctors to assess a person’s risk of developing certain cancers, based on information about their genetics and family background.
Predicting breast cancer risk
BOADICEA calculates a woman’s risk of breast cancer based on her family history. It also works out her likelihood of having a faulty version of one of the two ‘high risk’ breast cancer genes – BRCA1 and BRCA2. While rare (they’re responsible for fewer than 5 per cent of breast cancer cases), faulty versions of these genes can greatly increase a woman’s risk of developing breast or ovarian cancer.
The BRCA genes were identified by scientists (including some funded by Cancer Research UK in the 1990s). There are now genetic tests available for women with a strong family history of breast cancer that can spot certain known faults in BRCA1 and BRCA2.
But these tests aren’t perfect and ‘unknown’ faults can be missed. And also, for a variety of personal and practical reasons, not every woman will choose to undergo genetic testing for BRCA faults.
Enter BOADICEA, which can provide an estimate of the chance that a woman with a strong family history of breast or ovarian cancer will develop the disease.
A doctor can input information including a woman’s age, family history and any results from BRCA gene-tests, and BOADICEA will provide an estimate of her chance of developing the disease over her remaining lifetime.
How can this help?
Getting smarter at assessing people’s risk of cancer could have a big effect on the way we run our screening programmes. Currently, women between 50 and 70 are invited to have a mammogram – and the Government is planning to expand this NHS programme to cover women between 47 and 73 by 2012.
But younger women who are at increased risk of breast cancer because of their inherited genes could be offered extra screening to monitor them closely for early signs of the disease.
For example, National Institute of Clinical Excellence (NICE) guidelines recommend that women aged 30-49 with a faulty BRCA1 or BRCA2 gene should be offered annual MRI screening.
But some women under 50 have a strong family history of breast cancer but no identifiable faults in their BRCA genes. This is where BOADICEA can also help – for these women, NICE recommends that doctors use the programme to identify women who have the greatest risks of developing breast cancer.
These women could be offered annual MRI screening regardless of whether they test positive for faulty BRCA genes.
BOADICEA could also help with genetic counselling, where individual risk assessments can help women to weigh up their options. It could give them grounds for mulling over difficult decisions, such as whether to have surgery to remove breast and ovarian tissue, and what age might be best to do this.
And BOADICEA can also help doctors to target BRCA testing to those who are most likely to benefit. Since it can estimate the likelihood that a woman has a faulty version of BRCA1 or BRCA2, this helps to ensure that women with a high chance of having a faulty gene are referred for genetic testing – while reassuring those who are at lower risk and sparing them from unnecessary tests
With new funding from Cancer Research UK, Dr Antoniou is ‘fine-tuning’ BOADICEA to make it even more accurate – by taking into account more recently discovered low- and medium-risk genes (such as here and here). These increase a person’s risk of developing breast cancer to a lesser extent than BRCA1 or BRCA2, but faulty versions are far more common in the general population.
But while we’re discussing genetics, it’s important not to forget the influence that things in our lives can have on our risk of developing breast cancer – such as when we start or finish our periods, or whether we use the Pill or hormone replacement therapy. Dr Antoniou also plans to incorporate these into his programme as well.
BOADICEA can also provide a risk assessment for ovarian cancer based on family history and any BRCA testing. But groundbreaking studies are now uncovering low risk genes that increase the risk of ovarian cancer. As these discoveries continue over the next few years, Dr Antoniou will incorporate these into his programme to make it more accurate.
Not just for the ladies
Men aren’t out of the picture either. Faulty BRCA genes can also increase the risk of developing prostate cancer. And recent groundbreaking studies by Cancer Research UK scientists are identifying a number of low-risk variants for prostate cancer – here and here.
So with Cancer Research UK funding, Dr Antoniou is also developing a brand new programme to estimate a man’s risk of developing prostate cancer. Again, this could help identify those men who will most benefit from active monitoring for signs of the disease. Given the lack of clarity around PSA results such a tool would be a big step forwards.
On the horizon
Dr Antoniou’s research specifically focuses on those people with a strong family history of breast, ovarian or prostate cancer who are likely to have a faulty, and relatively rare, BRCA gene.
However, as we learn more and more about the combinations of low-risk genetic variations that influence our risk of certain cancers, the dream of assessing an ‘average’ person’s risk of cancer may soon become a reality.
But with this promise comes a need for caution. There are many commercial companies who already offer this type of genetic testing. But at this stage, we think it’s far too early to offer such services to the general population – as Laura wrote about last year.
Looking to the future, it’s exciting to be funding scientists like Dr Antoniou, and we hope his work will help make sense of the ever-growing volume of information about genes and cancer.
Alison Ross, Senior Science Information Officer