Low-Dose Aspirin, NSAIDs May Reduce Colorectal Cancer Risk

A new study finds a connection between long-term continuous use of low-dose aspirin and non-aspirin anti-inflammatory drugs (NSAIDs) and a lower risk of colorectal cancer.

In a population-based, case-control study of 10, 280 case patients and 102,800 control participants, researchers evaluated patients with first-time colorectal cancer in northern Denmark between the years 1994 and 2011, selecting population control participants by risk-set sampling. With the goal of assessing associations between the use of low-dose aspirin or other NSAIDs and cancer risk, investigators reviewed data on drug use, comorbid conditions, and history of colonoscopy, taken from prescription and patient registries. The use of low-dose aspirin (75 to 150 mg) and non-aspirin NSAIDs was defined according to type, estimated dose, duration, and consistency of use.
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The authors found that continuous long-term use of low-dose aspirin—5 years or longer—was associated with a 27% reduction in colorectal cancer risk. In addition, non-aspirin NSAID use was associated with a substantial reduction in colorectal cancer risk, particularly for long-term, high-intensity use—an average defined daily dose greater than or equal to 0.3—of agents with high cyclooxygenase-2 selectivity. (The authors note that data was not available for over-the-counter purchases of high-dose aspirin and low-dose ibuprofen or NSAID dosing schedules, there were several comparisons, and that they were unable to adjust for confounding by some risk factors.

These results demonstrate that, if taken at doses of 75 to 150 mg, long-term, continuous aspirin use is “necessary to achieve a substantial protective effect against colorectal cancer,” says Søren Friis, MD, senior scientist and associate professor at the Danish Cancer Society Research Center, and lead author of the study.

While other studies have found a similar risk reduction, “what’s new is that our findings indicate that, unless aspirin is taken continuously for 5 or more years, there is practically no effect against colorectal cancer,” says Friis. “So, the idea that all persons in the general population should take aspirin for 5 to 10 years to achieve a protective effect against colorectal cancer or other cancer types is not readily appealing, because of the risk of accumulating side effects during this treatment period.”

However, “the benefit/risk profile seems to tip in favor of offering treatment with low-dose aspirin to high-risk individuals for colorectal cancer,” he says, “including patients with a familial disposition or hereditary conditions for colorectal cancer, previous history of colorectal adenomas or cancer, and perhaps obese patients, [who are] also at increased risk of cardiovascular disease.”

Aspirin therapy, even at low doses, may be associated with serious adverse events, including upper gastrointestinal bleeding, and, more seldomly, hemorrhagic stroke, and no chemopreventive long-term treatment with aspirin should be started [without] consulting a physician, e.g., a general practitioner who can supervise the treatment, adds Friis. “Self-medication with aspirin or other potential chemopreventive drugs is strongly discouraged, because of the risk of serious adverse events.”

—Mark McGraw

Reference

Friis S, Riis A, et al. Low-Dose Aspirin or Nonsteroidal Anti-inflammatory Drug Use and Colorectal Cancer Risk. Ann Intern Med. 2015.