You are mutating. As you read this, somewhere in your body mistakes are being made as cells copy their DNA or repair damage from, say, cosmic rays. The vast majority of these mutations don’t matter. But occasionally a cell will acquire mutations that knock out key genes that limit growth, enabling runaway replication that leads to tumours.
Cancers, in other words, are very much genetic diseases. That is why the UK’s chief medical officer Sally Davies has this week that will focus on tackling cancer as well as rare diseases.
But should the UK’s cash-strapped National Health Service really be going all out on genomics when the field is still very much in its infancy?
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It is fast becoming routine to test tumour cells taken from patients for specific mutations that make them vulnerable – or resistant – to specific treatments. Sequencing the genomes of tumours could save time and money by replacing multiple genetic tests, Davies’s report suggests.
But it could instead turn out to be more expensive, once you factor in the cost of not just the sequencing but also of handling and analysing the huge amounts of data such tests produce.
Then there are the rare – usually inherited – diseases that collectively affect around 3 million people in the UK. For some people it can take 30 years to be correctly diagnosed. In the next five years, Davies wants most rare diseases to be diagnosed within weeks of being suspected, with the help of genome sequencing. Even if this ambitious goal can be achieved, however, there are no treatments for many of these diseases.
Personalised prevention
These limitations mean we should not be rushing to adopt whole-genome sequencing until it can be shown to produce better outcomes for these patients. But Davies’s report suggests the NHS should go even further, using genomics to prevent common diseases by looking at individuals’ particular risks.
“Policy makers should be under no illusion that the genomics revolution has made personalised prevention a reality,” the report says.
Perhaps the most famous example of this is Angelina Jolie opting for a double mastectomy after discovering she had mutations that greatly increased her risk of breast and ovarian cancer. But mutations with such a strong effect are very much the exception.
In most cases, sequencing the genomes of healthy people will not reveal any clear risks. That is partly because we still know so little about the influence of genes on health, but also because the causes of common disorders like heart attacks are turning out to be far more complex than we thought.
The worry is that the NHS could create a huge amount of work for itself, and needless stress for patients, if it starts telling healthy people about risks based on genetics tests.
Using genomics in this way is a form of screening. Doctors and patients alike tend to assume more tests mean more lives saved, but there is actually a long history of screening programmes doing more harm than good. The trouble is that many people picked out by such programmes get dosed up to the eyeballs with dangerous drugs and diced up by surgeons, only for it to turn out that they have, say, a benign tumour that would not have stopped them living a long and healthy life.
The golden rule of screening is not to introduce it unless randomised controlled trials have proved its worth. That is likely to be especially true of genomics, because it yields such vast amounts of poorly understood data.
What’s worrying is that the NHS push to embrace genomics is not just about helping patients. Part of the aim is to stimulate “a vibrant UK genomics industry”. If the drive to improve patient care has this as a side effect, that’s fine. The danger is that it becomes the primary aim, to the detriment of patients.
