16 Jul 2015

Prostate cancer in your genes: what can genetic testing tell us?

New advances in genetic medicine have been hitting the headlines a lot recently. And debates around the pros and cons of genetic testing, and what that could mean for preventing disease and creating personalised treatments have spiked this year. Sophie Lutter explores the ins and outs of genetic testing for prostate cancer, and what it might mean for men and their families, in terms of improving treatment and identifying those at risk.

The first description of the DNA double helix in 1953 sparked a revolution in the way we view and understand ourselves and the world we live in. Our genome, that is our entire DNA sequence, and our ever-growing understanding of it, is an immensely powerful thing. It brings possibilities for understanding, fighting and preventing disease – including some prostate cancers.

These possibilities become more likely with every new discovery that confirms prostate cancer isn’t a single disease, but thousands of different diseases. As one scientist put it recently: “How many different prostate cancers are there? How many men with prostate cancer are there? It’s the same thing.”

Many conditions now use genetic testing to match patients to the best possible treatment. Recent research has shown that this type of matchmaking might be possible in prostate cancer too. 

What do we mean by genetic testing?

Genetic testing involves looking at an individual’s DNA to find out what order their DNA molecules are put together in. The variations in this order, or sequence, are what makes each of us unique. But when people say ‘genetic testing’ it can mean slightly different things.

There are two main types of genetic testing.

Firstly, there’s genetic testing to look at the specific DNA in a person’s cancer cells. This may or may not be different to that of their ‘normal’ cells, and can help clinicians understand that person’s cancer better. Sometimes it can also help them to select the best treatment for that particular patient.

Secondly, there’s genetic testing to look at the genes in normal cells, to find any genetic changes you’ve inherited from your parents, which may increase your risk of cancer or other diseases.

As well as these two types of testing, there are also different techniques that can be used. First, there’s something called whole genome sequencing. This means looking at a person’s complete DNA sequence for any and all variations from what’s expected.

Alternatively, genetic tests can look specifically for known mutations linked to a disease, rather than fishing through the entire genome. This is usually what we mean when we talk about genetic testing for prostate cancer.

We already know that not all drugs work for everyone, and genetic testing could be an essential tool to find out who will respond best to a particular treatment and which treatments might work best for each individual. Scientists also hope to one day use genetic changes in cancer DNA to find out when a treatment stops working. This could save precious time for patients and save money as people can switch earlier to new treatments that have a better chance of working.  

Using genetic testing to predict prostate cancer risk

Whether it was Voltaire, Winston Churchill or someone else who said it, the words ‘with great power comes great responsibility’ have never been truer. There are many benefits of genetic testing and personalised medicine for people who’ve already been diagnosed with a disease. However, there are still serious questions to consider when it comes to using genetic testing for diagnosis, screening and prevention. 

We spoke to Sarah Rose, a genetic counsellor at Guy’s and St Thomas’ Hospital to ask about some of the issues she deals with on a daily basis. She said: “Genetic testing is available for men with, or at risk of, prostate cancer on the NHS, but only for men with a very strong family history of prostate, breast and/or ovarian cancer.

“These are the cancers most strongly linked to BRCA1 or BRCA2 mutations, which are the only known ‘prostate cancer’ genes we can test for inherited mutations at the moment. This is because we can only offer testing when we know what the associated risk of a particular gene mutation is, and what to do with the information. There’s no point offering a whole genome test if we don’t know what to say about the results.

“Of course some people do have a strong family history, but don’t have a BRCA mutation, although they may have mutations in other genes that we can’t test for. Instead, we can refer them to various research trials, like the UK Genetic Prostate Cancer Study, which is looking for other genetic changes associated with prostate cancer. 

“When we find a BRCA mutation, we then offer testing to all family members. Most of the men we see with prostate cancer who have a BRCA mutation are less concerned for themselves than for their children – especially their daughters – because of the risks of breast and ovarian cancer.

“Deciding whether or not to have a genetic test is not straightforward. It’s a very personal decision. We also encourage people to be open with their children about their genetic risk, otherwise it can be hard to talk to them when they’re older – they may feel like they’ve been lied to, or important information has been kept from them.

“Genetic counselling can help people think about their options around testing. We can explain the risks and the implications of testing, and help people consider the impact on themselves and their family. We’re there to offer support to patients, their partners and families throughout. We try to help people deal with the emotional impact of testing – some people feel guilty for having a mutation and passing it on, even though there’s no question of fault. We also try to make sure people don’t regret their decision to get tested, and that they’re doing it for the right reason – because they want to – not because of family pressure. 

“We also keep in touch with our BRCA families to make sure that we share the latest information and research opportunities with them – science is moving so fast that things might change at any time.” 

When will genetic testing be available to all men?

Before we can get to a point where genetic testing can be rolled out on a large scale, there are likely to be quite a few practical barriers to overcome. 

An obvious one would be making the testing technology cheap enough. But we would also need to confirm the benefits of genetic testing for prostate cancer risk, and who should be tested. For example, most prostate cancers aren’t caused by a single genetic mutation, so it wouldn’t necessarily make sense to test everybody. And since we don’t yet know how to prevent prostate cancer developing, we still need to know more about the benefits of genetic testing even for men with a family history of prostate cancer. 

Professor Ros Eeles at the Institute of Cancer Research is leading two clinical trials that are designed to answer these questions. The IMPACT trial is asking whether regular monitoring of men with a BRCA1 or BRCA2 mutation leads to earlier diagnosis of aggressive prostate cancer. And in The PROFILE trial, researchers will use existing genetic tests and family history to try and find men at high risk of prostate cancer so that they can also be regularly monitored. They will compare rates of prostate cancer diagnosis between men considered to be at high and low genetic risk of prostate cancer. 

In addition, the relevant parts of the health care system would need to be brought up to speed to support increased testing. For example, more genetic counsellors would need to be recruited, and/or more doctors would need to be trained in how to talk to people about the possible consequences of being tested and explain results. 

Protecting privacy – who should know the result?

Of course there’s no question that as with all medical information, genetic data needs to be kept securely, and there need to be rules in place to govern who can have access to such sensitive information. But the stakes could be really high with genetic information. If insurance companies and banks were allowed to use your genetic status in their assessments, there could be implications for health, travel and life insurance, as well as for your credit rating or ability to get a mortgage. 

There could be implications for employment too. As part of a recent YouGov survey for the Astellas Innovation Debate, one in five bosses (around 22 per cent) admitted that if an employee revealed his or her greater genetic risk of serious illness, they’d also be at higher risk of redundancy and be deemed less eligible for promotion. So it’s just as well that at the moment, European legislation denies employers access to their employees’ genetic data, and prevents insurance companies from demanding it.

What do you think?

Knowing you have a genetic predisposition to prostate cancer might mean that you monitor your health more closely, so may be diagnosed earlier. On the other hand, it might mean that you spend years worrying about getting a disease that might never develop. It’s not a straightforward issue, so we want to know what you think about it. 

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