One aspirin a week slashes the risk of digestive-tract cancers by more than a third

Popping just one aspirin a week could reduce a person’s digestive cancer risk by more than a third, research suggests.

The painkiller has long been thought to protect against liver tumours, however, its effect on other forms of the disease was less clear.

To learn more, scientists from The Mario Negri Institute for Pharmacological Research in Milan looked at 113 studies investigating a link between aspirin and different types of cancer.

Results suggest taking the pill once or twice a week could reduce a person’s risk of digestive-tract cancers by up to 39%.

This includes notoriously difficult-to-treat forms of the disease, like pancreatic tumours.

Although unclear, aspirin may inhibit the enzyme cyclooxygenase, which is linked to the onset of cancer and tumour growth.

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The scientists looked at more than 100 studies published up to 2019.

Of these, 45 trials analysed how aspirin affects the risk of bowel cancer.

The remainder investigated head and neck cancer, as well as various tumours of the digestive tract, including the oesophagus, stomach and liver.

Results – published in the Annals of Oncology – suggest “regular use of aspirin”, defined as at least one or two tablets a week, reduced the risk of gastric cardia cancer by 39%.

The gastric cardia is the point where the oesophagus opens into the stomach. It is unclear how many of these cancer cases arise a year.

Aspirin use was also found to reduce the risk of hepatobiliary cancer by 38%. This refers to tumours of the liver or bile ducts.

The odds of developing cancer of the stomach, oesophagus, bowel or pancreas was cut by 36%, 33%, 27% and 22%, respectively.

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No link was found between taking aspirin and the onset of head and neck cancer.

“There are about 175,000 deaths from bowel cancer predicted for 2020 in the EU, of which about 100,000 will be in people aged between 50 and 74,” said study author Dr Carlo La Vecchia.

“If we assume regular use of aspirin increases from 25% to 50% in this age group, this would mean that between 5,000 to 7,000 deaths from bowel cancer and between 12,000 and 18,000 new cases could be avoided if further studies show aspirin does indeed cause the reduction in cancer risk.

“Corresponding figures would be approximately 3,000 deaths each for oesophageal, stomach and pancreatic cancer, and 2,000 deaths from cancer of the liver.”

The scientists also looked at the effect of aspirin dose, and how often it is taken, on bowel cancer specifically.

“We found the risk of cancer was reduced with increased dose,” said lead author Dr Cristina Bosetti.

“An aspirin dose between 75 and 100mg a day was associated with a 10% reduction in a person’s risk of developing cancer compared to people not taking aspirin.

“A dose of 325mg a day was associated with a 35% reduction and a dose of 500mg a day was associated with a 50% reduction in risk.”

The scientists stressed the higher aspirin dose result was based on just a few studies and should “be interpreted cautiously”.

“Compared to people who did not take aspirin regularly, the risk of bowel cancer declined in regular aspirin users up to 10 years,” said Dr Bosetti.

“The risk was reduced by 4% after one year, 11% after three years, 19% after five years and 29% after ten years.”

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The scientists were particularly encouraged by their results on pancreatic cancer. Just 5% of patients survive 10 years or more after their diagnosis in England and Wales.

“The findings for pancreatic and other digestive tract cancers may have implications for the prevention of these highly lethal diseases,” said Dr La Vecchia.

“For pancreatic cancer, we found that risk of the disease declined by 25% after five years among people who took aspirin regularly compared to those who did not.”

The scientists stress aspirin should only be taken regularly after a consultation with a doctor, who will take into account the individual’s cancer risk factors.

“This includes factors such as sex, age [and] a family history of a first-degree relative with the disease”, said Professor La Vecchia.

“People who are at high risk of the disease are most likely to gain the greatest benefits from aspirin.”

Aspirin is often recommended as a blood thinner for people at risk of a heart attack or stroke.

Warding off clots can trigger side effects, however, including bleeding into the stomach or brain.