- Those who use proton pump inhibitors twice as likely to develop stomach cancer
- Risk of cancer increases the longer the drugs are used, scientists claim
- Suspected the pills create gastrin which triggers growth of cancerous cell
Indigestion pills taken by millions of Britons significantly increase the risk of stomach cancer, a major study has found.
Scientists say people who regularly use proton pump inhibitors (PPIs) – common drugs used to treat acid reflux – are twice as likely to develop the cancer.
And if people took the drugs long-term, the risk soared, rising five-fold after a year to more than eight-fold after three years of regularly taking the pills.
The scientists, from University College London and the University of Hong Kong, suspect the pills stimulate a hormone called gastrin, which triggers the growth of cancerous cells.
More than five million bottles and packets of PPIs – which include omeprazole and lansoprazole – are prescribed each year in England to treat gastroesophageal reflux, a severe form of heartburn. Many more Britons buy them over the counter at pharmacies without a prescription, or in corner shops and supermarkets.
The drugs are not recommended for long-term use, but doctors fear that because they are so readily available, people may take them without medical supervision for years.
Fears are growing about the health impacts of the drugs if taken for too long, with recent research linking sustained use to dementia, heart attacks and kidney problems. The new research, published in the BMJ journal Gut, involved 63,000 people in Hong Kong. At the beginning of the study, they were treated with antibiotics to kill bacteria called H. pylori, which is linked to stomach cancer.
The researchers did this to rule out the role of bacteria in the development of cancer, increasing their confidence that the PPI drugs were to blame.
The patients were then tracked for an average of seven years.
Researchers found that those who took the pills at least weekly were more than twice as likely to develop stomach cancer during the study period compared to those who did not use the drugs.
For daily users, the risk increased 4.5 times, and the longer people used the drugs, the greater their risk, rising to an 8.3-fold greater risk for those who took the pills daily for at least three years.
People who took an alternative indigestion treatment called H2 blockers saw no increased risk.
The researchers stressed that while the relative risks are dramatic, few people get stomach cancer – also known as gastric cancer – so in absolute terms the threat is small. Out of the 63,397 people studied, only 153 (0.24 per cent) developed stomach cancer.
The researchers calculated that this means that for every 10,000 people who take PPIs, roughly eight people a year will develop stomach cancer – four more than if none was taking the pills.
They wrote: ‘We found that long-term use of PPIs increased the risk of gastric cancer development. There was a clear dose-response and time-response trend of PPIs uses and gastric cancer risk. Physicians should exercise caution when prescribing long-term PPIs.’
A spokesman for the Medicines and Healthcare products Regulatory Agency, in charge of drug safety in Britain, said: ‘PPIs available without prescription are only for short-term use and at low dose. Patient safety is of utmost importance and we keep all emerging evidence under review.’
But Professor Stephen Evans, of the London School of Hygiene & Tropical Medicine, criticised the findings, saying that people who take PPIs are more likely to be ill in the first place. He added: ‘The absolute risk is small. All effective drugs have unwanted effects, usually adverse, so it is possible that PPIs have gastric cancer as one on those unwanted effects, and this paper offers some possible evidence for this, but is by no means proof of a causal effect.’
The Proprietary Association of Great Britain, which represents manufacturers of over-the-counter medicine, said nobody should take PPIs for more than two weeks without speaking to a pharmacist.
Chief executive John Smith said: ‘The study only looked at prescription use of PPIs, which are typically used at higher doses and for longer durations. Long-term PPI users are also normally much older than non-users, and age was shown to be a significant risk factor in the development of gastric cancer.
‘PPIs available over the counter are intended for short-term use only and are an appropriately safe way to manage symptoms.’