Aspirin may be associated with a reduction in the risk of developing several cancers of the digestive tract. The largest and most comprehensive analysis to date of the link between aspirin and digestive tract cancers, published by Bosetti et al in Annals of Oncology, found reductions in the risk of these cancers of between 22% and 38%.
Aspirin has been linked to a reduction in the risk of colorectal cancer for some time, and other smaller analyses have found associations with cancers of the esophagus and stomach.
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Methods
This analysis looked at evidence from 113 observational studies investigating cancers in the general population published up to 2019. Forty-five of the studies were on colorectal cancer, with 156,000 cases included. In addition to colorectal cancer, cancers investigated included head and neck, esophageal, stomach, gastric cardia, liver, gallbladder, bile duct, and pancreatic cancers.
Results
The researchers found that regular use of aspirin—defined as taking at least one or two tablets a week—was associated with a significant reduction in the risk of developing all these cancers, excluding head and neck cancer.
Specifically, aspirin use was linked to a 27% reduced risk of colorectal cancer (45 studies), a 33% reduced risk of esophageal cancer (13 studies), a 39% reduced risk of gastric cardia (ten studies), a 36% reduced risk of stomach cancer (14 studies), a 38% reduced risk of hepatobiliary cancers (five studies), and a 22% reduced risk of pancreatic cancer (15 studies). Ten studies of head and neck cancer did not show a significant reduction in risk.
Senior study author Carlo La Vecchia, MD, Professor of Epidemiology at the School of Medicine, University of Milan, said, “There are about 175,000 deaths from colorectal cancer predicted for 2020 in the European Union, of which about 100,000 will be in people aged between 50 and 74 [years]. If we assume that 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 colorectal cancer and between 12,000 and 18,000 new cases could be avoided if further studies show that aspirin does indeed cause the reduction in cancer risk.”
“Corresponding figures would be approximately 3,000 deaths each for esophageal, stomach, and pancreatic cancer, and 2,000 deaths from [liver] cancer. Given the unfavorable prognoses for these cancers, the number of new cases would be only slightly greater,” said Dr. La Vecchia.
The researchers also analyzed the effect of aspirin dose and duration on colorectal cancer. They looked at low dose (100 mg), regular dose (325 mg) and high dose (500 mg), combined with how many times a day, week, or month it was taken.
Lead study author Cristina Bosetti, PhD, Head of the Unit of Cancer Epidemiology at the Mario Negri Department of Oncology, Milan, Italy, said, “We found that the risk of cancer was reduced with increased dose; an aspirin dose between 75 and 100 mg 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 325 mg a day was associated with a 35% reduction, and a dose of 500 mg a day was associated with a 50% reduction in risk. However, the estimate for high-dose aspirin was based on just a few studies and should be interpreted cautiously.
“Our findings on colorectal cancer support the concept that higher aspirin doses are associated with a larger reduction in risk of the disease. However, the choice of dose should also take into consideration the potential risk of stomach bleeds, which increases with higher aspirin doses. Compared to people who did not take aspirin regularly, the risk of colorectal cancer declined in regular aspirin users [for] up to 10 years. The risk was reduced by 4% after 1 year, 11% after 3 years, 19% after 5 years, and 29% after 10 years,” said Dr. Bosetti.
Dr. La Vecchia said: “Taking aspirin for the prevention of colorectal cancer, or any other cancers, should only be done in consultation with a doctor, who can take account of the person's individual risk. This includes factors such as sex, age, a family history of a first-degree relative with the disease, and other risk factors. People who are at high risk of the disease are most likely to gain the greatest benefits from aspirin.”
In addition to stomach bleeds, the side effects of aspirin include bleeding in other parts of the body and, occasionally, hemorrhages.
The study authors concluded, “The present comprehensive meta-analysis supports and further quantifies the inverse association between regular aspirin use and the risk of colorectal and other digestive tract cancers, including some rare ones. The favorable effect of aspirin increases with longer duration of use, and, for colorectal cancer, with increasing dose.”
Disclosure: For full disclosures of the study authors, visit annalsofoncology.org.
