Aspirin's anti-cancer actions depend on individual genetic make-up

Whether or not aspirin reduces a person's risk of bowel cancer could all be down to their genetic make-up, according to a US study.

The findings also suggest that aspirin may increase cancer risk in a minority of patients.

Dr Ulrike Peters, one of the study authors from the Fred Hutchinson Cancer Research Centre in Seattle told Cancer Research UK: '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.'

Identifying patients who do not respond to aspirin - a non-steroidal anti inflammatory drug (NSAID) - is important as long-term use of NSAIDs can cause severe side effects such as gastrointestinal bleeding. NSAIDs are sometimes prescribed for patients with a history of colon polyps - a condition that can lead to colon cancer.

The research team, led by Professor Hongmei Nan from Indiana University, conducted a meta-analysis combining the results of ten previous studies on NSAIDS conducted between 1976 and 2003, with a comparison of data from over 8,600 people who went on to develop bowel cancer with a similar number who did not.

The team analysed the DNA records of each patient, looking for genetic variants called single nucleotide polymorphism (SNPs) and found that certain SNPs correlated with patients who benefited from taking aspirin. However, one in ten participants who had a different SNP showed no benefit from taking aspirin at all. A further one in 25 with yet another SNP actually went on to develop bowel cancer after taking aspirin, although it is unclear if aspirin was the cause.

Professor Peter Rothwell, an expert in the health effects of aspirin at John Radcliffe Hospital in Oxford, UK who was not involved in the study, told Cancer Research UK: '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.'

If these results can be validated, then personalised treatments of cancer could follow in the future. Dr Richard Wender of the American Cancer Society wrote in an accompanying editorial: 'The ability to translate genetic profiling into tailored preventive care plans for individuals is still years away'. He later told Reuters, that he does 'anticipate the time when genome sequencing to determine a lifelong (colorectal-cancer) prevention and screening strategy is a reality'.

Colorectal cancer is the second leading cause of cancer death in the USA, according to the US National Cancer Institute. The study was published in JAMA.