Milan, Italy—A new meta-analysis offers more evidence of what has been suspected: Use of aspirin helps reduce the risk of several cancers of the digestive tract, including some with high fatality rates, such as pancreatic and liver cancers.

That’s according to a report in Annals of Oncology, which notes reductions in the risk of those cancers of between 22% and 38%.

The analysis, led by researchers from the Mario Negri Department of Oncology in Milan, Italy, examined evidence from 113 observational studies investigating cancers in the general population published up to 2019. Nearly half of the studies, 45, dealt with bowel cancer and included 156,000 cases. Other studies focused on cancers of the head and neck, esophagus, gastric system and stomach, liver, gallbladder, bile ducts, and pancreas.

Based on those findings, meta-analysis authors 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 of the cancers except head and neck.

Specifically, researchers determined that aspirin use was linked to:
• A 27% reduced risk of bowel cancer (45 studies),
• A 33% reduced risk of esophageal cancer (13 studies),
• A 39% reduced risk of gastric cardia (10 studies),
• A 36% reduced risk of stomach cancer (14 studies),
• A 38% reduced risk of hepato-biliary cancers (five studies), and
• A 22% reduced risk of pancreatic cancer (15 studies).

The 10 studies on head and neck cancer did not show a significant reduction in risk, however.

“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,” points out senior author Carlo La Vecchia, MD, of the University of Milan. “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 bowel 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 cancer of the liver. Given the unfavorable prognoses for these cancers, the number of new cases would be only slightly greater.”

The authors also looked at dosage and cancer risk reduction. “Our findings on bowel cancer support the concept that higher aspirin doses are associated with a larger reduction in risk of the disease,” explained lead author Cristina Bosetti, PhD, head of the Unit of Cancer Epidemiology at the Mario Negri Department of Oncology. “However, the choice of dose should also take into consideration the potential risk of stomach bleeds, which increases with higher aspirin doses.”

Preventive use of aspirin is not without risk, the researchers point out. In addition to stomach bleeds, the side effects of aspirin include bleeding in other parts of the body and, occasionally, hemorrhages, they note.

The authors also caution that their research is based on observational studies and should be confirmed in clinical trials.

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