Aspirin’s anti-cancer effects depend on a person’s genetic make-up
A person’s genetic make-up might determine whether they could benefit from taking aspirin to prevent bowel cancer, according to a US study.
The findings – published in the journal JAMA – also suggest that the drug could even increase cancer risk in a minority of people – although experts cautioned that more research was needed to confirm this.
"We really need to understand more about who will – and who won’t – benefit from taking aspirin before it can be recommended for widespread use to prevent cancer" - Dr Julie Sharp, Cancer Research UK
Certain forms of cancer are less common among people who take regular aspirin. But the debate over its relative risks and benefits has been ongoing for a number of years.
“Long-term use can lead to gastrointestinal bleeding and other side effects”, said Dr Ulrike Peters, from the Fred Hutchinson Cancer Research Center in the US, and one of the study authors.
“We wanted to investigate if genetic variation determined who is responding particularly well with aspirin - for whom aspirin use has particular benefit and for whom it doesn't.”
The team combined the results of several previous studies on aspirin and other similar drugs – collectively called non-steroidal anti-inflammatory drugs, or NSAIDs – comprising more than 8,600 people who went on to develop bowel cancer, and a similar number who remained healthy.
They then analysed participants’ DNA records, and looked at whether certain genetic variants, known as single-nucleotide polymorphisms, were more or less common in each group.
As well as confirming the overall benefits of aspirin in preventing the disease, they found that nearly one in 10 study participants (nine per cent) who had a particular genetic variation received no benefit from the drug.
And a further four per cent – one in 25 – who carried one of two other DNA variants appeared to have an increased likelihood of going on to develop bowel cancer after taking aspirin.
However, a leading aspirin expert cautioned that the findings needed further verification.
“The results of the study are interesting, but it pays to be cautious and we need to see confirmation in other studies,” said Professor Peter Rothwell, an expert in the health effects of aspirin based at John Radcliffe Hospital and the University of Oxford
“The genetic variants on which the findings are based are only present in four per cent of the population and so the number of people who carried them in the study will have been relatively small.
“In this situation, there is always a significant possibility of chance findings. So the result needs to be repeated in further studies – ideally in randomised controlled trials of aspirin – before it can be regarded as being valid,” he said.
The findings add further weight to the idea that – although aspirin has clear cancer-preventing effects – more work remains to determine who will benefit most.
Last year, an analysis of previous studies found that aspirin protects most strongly against bowel, stomach and oesophageal cancers and also, to a lesser extent, against lung, prostate and breast cancers.
The research estimated that, among 1,000 people aged 60 who took aspirin for 10 years, over the next 20 years there would be 16 fewer deaths from cancer overall, compared with 1,000 people who didn’t take the drug.
However, the analysis also found that there would be between two and three extra deaths from strokes, serious peptic ulcers and gastric bleeds.
“This study reinforces the idea that we really need to understand more about who will – and who won’t – benefit from taking aspirin before it can be recommended for widespread use to prevent cancer,” said Dr Julie Sharp, head of health information at Cancer Research UK.
“There are also several other outstanding questions, such as the best age to start – and stop – taking it, and what dose gives the best balance of benefits against risks.
"Aspirin could well play a role in cancer prevention in the future, but in the meantime if you’re considering taking it, you shouldn’t do so without discussing it with your GP first, as it can have serious side effects in some people,” she added.
- Recently on our blog: Aspirin and cancer - nearly but not quite
- Nan H., Hutter C.M., Lin Y., Jacobs E.J., Ulrich C.M., White E., Baron J.A., Berndt S.I., Brenner H. & Butterbach K. & Association of Aspirin and NSAID Use With Risk of Colorectal Cancer According to Genetic Variants., JAMA, PMID: http://www.ncbi.nlm.nih.gov/pubmed/25781442