Aspirin Use Tied to Reduce Risk of Multiple Cancers

While used for decades for prevention of cardiovascular events, new research from a team of European investigators links use of aspirin to a reduction in the risk of multiple cancers of the digestive tract.

Results of the systematic review and meta-analysis, which included data from more than 100 observational studies, suggested taking aspirin as little as once or twice a week could reduce risk of half a dozen cancers including stomach, liver, and pancreatic cancers, but aspirin use had no impact on reducing cancers of the neck or head.

"These findings suggest there's a beneficial effect of aspirin in the prevention of bowel and other cancers of the digestive tract,” said lead investigator Carlo La Vecchia, MD, Professor of Epidemiology at the School of Medicine, University of Milan, in a statement. “The results for bowel, esophageal and pancreatic cancers are consistent with evidence from clinical trials on aspirin in the prevention of heart and blood vessel diseases.”

With the debate over the role of aspirin in cancers of the digestive tract still ongoing, La Vecchia and colleagues designed the largest analysis of its kind to in an effort to bring further clarity to the subject. Using PubMed/Medline, Embase, and the Cochrane Library, investigators identified 113 observational studies investigating aspirin use and cancer risk published between 2011 and March 2019.

For inclusion in the analysis, studies had to meet multiple criteria such as providing information on aspirin use, being focused on at least 1 of 14 major malignant neoplasm, and needing to report relative risk (RR) estimates and the corresponding 95% confidence interval or provide enough data to calculate them. Of note, investigators defined low dose aspirin use as 75-100 mg, regular dose as 325 mg, and high dose as 500 mg—they also analyzed use by daily dose as well as frequency and duration of use.

Of the 113 studies included, 45 examined colorectal cancer, 15 examined pancreatic cancers, 14 examined stomach cancer, 13 examine squamous-cell esophageal cancers, 10 examined esophageal and gastric cardia adenocarcinoma, 10 examined cancers of the head and neck, and 5 examined hepato-biliary cancers.

Upon analysis, aspirin use was associated with a 27% reduced risk of colorectal cancers (RR, 0.73; 95% CI, 0.69-0.78), a 33% reduce risk of squamous-cell esophageal cancer (RR, 0.67; 95% CI, 0.57-0.79), a 39% risk of esophageal and gastric cardia adenocarcinoma (RR, 0.61, 95% CI, 0.49-0.77), a 36% reduced risk of stomach cancer (RR, 0.64; 95% CI, 0.51-0.82), a 38% reduced risk of hepato-biliary cancers (RR, 0.62; 95% CI, 0.44-0.86), and a 22% reduced risk of pancreatic cancers (RR, 0.78; 95% CI, 0.68-0.89).

Additionally, results of the analysis indicated a potential association between aspirin dosage and risk of colorectal cancers. Specifically, results suggest low-dose aspirin reduced risk by 10%, regular dose reduced risk by 35% and high-dose aspirin reduced risk by 50%.

La Vecchia and fellow investigators also noted it is important to remember the risk of adverse events that accompanies regular use of aspirin. In the aforementioned statement, La Vecchia cautions the results are based on observational data and patients should consult clinicians before initiating aspirin therapy to reduce risk of cancers.

"Taking aspirin for the prevention of bowel cancer, or any other cancers, should only be done in consultation with a doctor, who can take account of the person's individual risk,” said La Vecchia. “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."

This study, “Aspirin and the risk of colorectal and other digestive tract cancers: an updated meta-analysis through 2019,” was published in the Annals of Oncology.