Taking aspirin a few times each week, or regularly for years decreases the risk of stomach cancer.
The ancient Greeks were well aware of the power of willow bark powder to relieve headaches, pain and fever. But not even Hippocrates, widely considered the father of Western medicine and whose records speak of the use of willow bark in ancient times, would have been aware of aspirin’s cancer-fighting properties.
In recent years, aspirin and other non-steroidal anti-inflammatory drugs have been shown to reduce death rate from multiple types of cancer by around 20 per cent. Studies have found that aspirin decreases the risk of developing cancers of the breast, skin, colon and oesophagus – the muscular tube that delivers food from the mouth into the stomach.
A study published this week in the journal PLoS ONE extends this already impressive list to include stomach (gastric) cancer – a cancer that can have a particularly poor outcome, as it is often diagnosed late. Researchers from three Chinese institutions – Guangdong Pharmaceutical University, Southern Medical University and Liuzhou Municipal Maternity and Child Healthcare Hospital – combined data from all published reports that had previously investigated the link between aspirin use and stomach cancer prevention. By pooling results in this way, the team were able to conduct what’s known as a meta-analysis, a standard form of analysis that can provide better evidence of a treatment’s effectiveness than any individual study.
The analysis showed that taking aspirin just once a week reduced the risk of developing stomach cancer by 10 per cent. Taking aspirin more frequently increased the benefit, but only up to a point. Aspirin twice a week reduced cancer risk by 19 per cent, and 4.5 times a week by 29 per cent, but increasing the frequency more than that saw the benefits gradually disappear.
The length of time that aspirin is regularly taken also appears to have an impact on cancer risk. The longer the period of aspirin use, the better the protection. In the analysis, four years of aspirin use was projected to decrease the risk of developing stomach cancer by 10 per cent. This increases to 19 per cent after 8 years, and 28 per cent after 12 years.
The mechanism behind aspirin’s cancer-curbing properties remains a mystery, although a small study of patients with the condition Barrett’s oesophagus – a common precursor to oesophageal cancer – may have identified a crucial piece of the puzzle. Scientists lead by Carlo Maley at the Center for Evolution and Cancer at the University of California, San Francisco, tracked cellular and genomic changes in the oesophagus of 13 patients, for an average of 12 years.
In Barrett’s oesophagus, cells of the oesophagus are damaged, usually due to acid reflux, and are at increased risk of becoming cancerous. Cancerous cells bear little resemblance to their healthy counterparts, having accumulated numerous mutations, known as somatic genome abnormalities, or SGAs, on their path to malignancy. The researchers found that once patients started taking aspirin, their oesophagus stopped accumulating SGAs as quickly; mutation rate was reduced by 90%.
Whatever the mechanism or mechanisms at play, the mounting evidence is that aspirin’s cancer-preventing credentials are real, and for an increasing number of cancer types.
- Ye X, Fu J, Yang Y, Gao Y, Liu L & Chen S. (2013). Frequency-risk and duration-risk relationships between aspirin use and gastric cancer: a systematic review and meta-analysis. PLoS ONE doi:10.1371/journal.pone.0071522
- Kostadinov RL, Kuhner MK, Li X, Sanchez CA, Galipeau PC, et al. (2013). NSAIDs modulate clonal evolution in Barrett’s esophagus. PLoS Genet. doi:10.1371/journal.pgen.1003553