An up-to-date meta-analysis investigated the relationship between regular aspirin consumption and cancers of the digestive tract sites. The review included 113 observational studies published up to March 2019, containing 45 colorectal cancer studies, and other common cancers like head and neck, esophageal, stomach, gastric cardia, liver, gallbladder, bile duct, and pancreatic cancers. The main objective of the study was to determine the link between aspirin and cancers of the digestive tract, and the effect of aspirin dose and its duration of use on colorectal cancer. Taken together, findings for gastrointestinal and colorectal cancer were consistent with the results from other clinical trials examining the role of aspirin towards the prevention of heart and blood vessel diseases. The meta-analysis highlighted the beneficial effect of aspirin for reducing the rates of certain cancers of the digestive tract.
Aspirin is presently emerging as an effective chemoprotective agent for colorectal cancer, and possibly a few other cancers.1,2 In Hong Kong, long-term usage of aspirin demonstrated significantly lower risks of oesophageal cancer, liver cancer, pancreatic cancer, stomach cancer, colorectal cancer, lung cancer, and leukaemia.3
Moreover, there are numerous randomized controlled trials (RCTs) and meta-analyses linking the usage of aspirin to decreased rates of colorectal cancer and gastrointestinal cancer.1,2,3 Despite these studies supporting the role of aspirin in reducing cancers at the digestive tract sites, currently, there is a lack of quantitative data for that. Furthermore, there is no information about the optimal dose and duration of aspirin use required to prevent bowel cancers.
Lead study author, Cristina Bosetti, Head of the Unit of Cancer Epidemiology at the Mario Negri Department of Oncology, Milan, Italy, led a systematic review of 113 recent studies covering more than 210,000 cancer patients. The aim was to ascertain the quantification of RR, the optimal dose and duration of aspirin use needed to suppress colorectal cancer and other gastrointestinal cancers. The meta-analysis examined aspirin’s capacity by firstly estimating the pooled RR of cancer for regular aspirin use versus non-aspirin use using random-effects models. Subsequently, for cancers with sufficient information, the linear and nonlinear relations between daily dose and duration of aspirin consumption, and the log-RR of cancer were examined.4
The meta-analysis revealed that regular consumption of aspirin is related to the decreased risk of colorectal cancer (RR=0.73; 95% CI: 0.69-0.78; n=45), squamous-cell esophageal cancer (RR=0.67; 95% CI: 0.57-0.79; n=13), adenocarcinoma of the esophagus and gastric cardia (RR=0.61; 95% CI: 0.49-0.77; n=10), stomach cancer (RR=0.64; 95% CI: 0.51-0.82; n=14), hepato-biliary tract cancer (RR=0.62; 95% CI: 0.44-0.86; n=5), and pancreatic cancer (RR=0.78; 95% CI: 0.68-0.89; n=15). However, no effect was observed for head and neck cancer (RR=0.94; 95% CI: 0.76-1.16; n=10). Risk estimates were consistent across location, gender and defined variables.4
Based on the findings from the 150,000 colorectal cancer case studies, patients receiving aspirin experienced a decline in risk by 25%. Besides, these cancer risks were inversely related to the dose and duration of aspirin used. As demonstrated over time, the risk of colorectal cancer lessens by 4% after 1 year, 11% after 3 years, 19% after 5 years and 29% after a decade.4
Importantly, Dr. Bosetti and her colleagues have determined the optimal dosage of aspirin required for minimizing colorectal cancer risk. Dr. Bosetti commented, “We found that the risk of cancer can be reduced with increased dose; 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.” She also mentioned that the results should be interpreted cautiously due to the lower number of studies used in the estimate.
Likewise, aspirin use is also inversely related to esophageal, stomach, liver, and pancreatic cancer and all neoplasms, except head and neck cancer.4
Findings from the current meta-analysis align with past meta-analyses in highlighting the beneficial effect of aspirin on the prevention of colorectal and other cancers of the digestive tract. The findings also suggest that increasing the dosage and duration of aspirin intake might be implicated in the decreasing rates of colorectal cancer and gastrointestinal cancer.