Bathroom cabinet staple aspirin could help prevent oesophageal cancer among those at a high risk of the disease, new research suggests.
Patients living with Barrett's oesophagus - a condition linked to chronic acid reflux - are more likely to go on to develop the cancer, which kills thousands in the UK every year.
Regularly taking a high dose of anti-acid reflux medication and a low dose of aspirin could help reduce this risk, according to the results of a Cancer Research UK-funded study.
Patients who used this over-the-counter medicine combination for at least seven years were around 20% less likely to develop oesophageal cancer than if they had been untreated, the research found.
Professor Janusz Jankowski, lead author of the study, said: "Our results are very exciting. Oesophageal cancer is hard to diagnose and hard to treat.
"So, we're pleased that such a cheap and well-established medicine can prevent and, or, delay development of cancer for these patients.
"Our hope is that this may also offer an opportunity to prevent esophageal cancer in wider populations."
However, experts stressed only those with diagnosed Barrett's oesophagus, not those who experience mild acid reflux, should consider the treatment.
The findings have been presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago.
Barrett's oesophagus, a changing of the cells in the lining of the food pipe, is partly linked to genetics and aggravated by acid reflux, experts believe.
Patients with the rare condition are at around a 50% greater risk of oesophageal cancer, Cancer Research UK said.
While just 2% go on to develop the disease, of those who do only 12% will survive for more than 10 years.
The AspECT trial tracked more than 2,500 people with Barrett's oesophagus from British and Canadian hospitals for around nine years.
Patients were split into four groups and given high or low dose of widely used Proton Pump Inhibitor (PPI) esomeprazole, which reduces the production of stomach acid, with or without a low dose of aspirin.
The most effective treatment was a high dose of the PPI and a low dose of aspirin, the study found, followed by a high dose of esomeprazole.
Dr Justine Alford, from Cancer Research UK, said: "It's important to remember that even though you can buy it over the counter, aspirin can have serious side effects like internal bleeding, so anyone thinking of taking regular aspirin should chat to their doctor first.
"Oesophageal cancer can be hard to diagnose at an early stage and so can be hard to treat. There hasn't been a significant improvement in survival for decades.
"Cancer Research UK has therefore identified oesophageal cancer as a cancer of unmet need, along with brain tumours, lung cancer, and pancreatic cancer."
Professor Jankowski, a consultant clinical adviser at the National Institute for Health and Care Excellence (Nice) and deputy vice chancellor of the Royal College of Surgeons in Ireland, said: "Based on these data, we believe people with heartburn should talk with their doctor about their risk of Barrett's esophagus, but they should not self-medicate with these medications."
Dr Andrew Epstein, a clinical oncologist at Memorial Sloan Kettering Cancer Center in New York City - speaking as an expert for ASCO, stressed that the results only apply to those with the diagnosed chronic acid reflux condition.
He said: "Should anyone with heartburn, even if its long-term heartburn do this? No. The data do not bear that out."
Smoking, drinking and diet are other known risk factors for oesophageal cancer.
It is the 13th most common cancer in the UK, with 9,000 new cases and 7,900 deaths every year.