Regular aspirin use may reduce risk for colorectal, other digestive tract cancers
Regular use of aspirin appeared to reduce the risk for several digestive tract cancers, according to results of a meta-analysis published in Annals of Oncology.
Researchers observed increased benefit with longer duration of use, and increased doses appeared to further reduce risk for colorectal 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 [years],” Carlo La Vecchia, MD, professor of epidemiology at University of Milan School of Medicine in Italy, said in a press release. “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 [due to] cancer of the liver,” he added. “Given the unfavorable prognoses for these cancers, the number of new cases would be only slightly greater.”
Aspirin has been associated with reduced risk for colorectal cancer and perhaps a few other cancers of the digestive tract. However, the degree of risk reduction and optimal dose and duration of aspirin use to prevent these cancers remain unclear, according to researchers.
Bosetti and colleagues conducted a systematic review and meta-analysis of all observational studies on aspirin and digestive tract cancers published through March 2019. Researchers used random effects models to estimate the pooled RR of cancer with regular aspirin use (at least one to two tablets per week) vs. nonuse and investigated dose- and duration-risk relationships when possible.
The meta-analysis included data from 113 studies, including 45 that looked specifically at colorectal cancer risk and included 156,019 cases.
Results showed associations between regular aspirin use and reduced risk for colorectal cancer (RR = 0.73; 95% CI, 0.69-0.78; n = 45 studies), squamous cell esophageal cancer (RR = 0.67; 95% CI, 0.57-0.79; n = 13 studies), adenocarcinoma of the esophagus and gastric cardia (RR = 0.61; 95% CI, 0.49-0.77; n = 10 studies), stomach cancer (RR = 0.64; 95% CI, 0.51-0.82; n = 14 studies), hepato-biliary tract cancer (RR = 0.62; 95% CI, 0.44-0.86; n = 5 studies) and pancreatic cancer (RR = 0.78; 95% CI, 0.68-0.89; n = 15 studies).
However, regular aspirin use did not appear associated with reduced risk for head and neck cancer (RR = 0.94; 95% CI, 0.76-1.16; n = 10 studies).
Researchers observed somewhat stronger associations in case-control studies compared with cohort and nested case-control studies. Risk estimates appeared consistent across selected covariates, including sex and geographical area.
Researchers also found that an aspirin dose of 75 mg to 100 mg per day conferred a 10% reduction in risk for colorectal cancer, whereas a dose of 325 mg per day conferred a 35% reduction and a dose of 500 mg per day conferred a 50% reduction. The estimate for high-dose aspirin should be interpreted with caution because it is based on only a few studies, according to researchers.
Results also showed inverse duration-risk relationships between aspirin use and all neoplasms except head and neck cancer.
The inherent biases of observational studies served as a limitation to this study.
“These findings suggest there’s a beneficial effect of aspirin in the prevention of bowel and other cancers of the digestive tract,” La Vecchia said in the release. “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.”
“The findings for pancreatic and other digestive tract cancers may have implications for the prevention of these highly lethal diseases,” he added. “For pancreatic cancer, we found that risk [for] the disease declined by 25% after 5 years among people who took aspirin regularly compared to those who did not.” – by John DeRosier.
Disclosures: A grant from Bayer AG supported this study. The authors report no relevant financial disclosures.