Colon cancer (CRC) is the second leading cause of cancer death in the United States. There is compelling evidence that screening for early CRC to find and remove precancerous polyps can reduce CRC mortality. However, screening is fraught with harm, including procedural complications and inherent limitations. For example, colonoscopy, the most widely used screening tool in the United States, is less effective than cancers of the left or descending colon in preventing cancers of the right or ascending colon.
Additionally, only 60% of US adults recommended for screening actually follow. Even in the best of circumstances, screening is resource-intensive, requires time, equipment, and a trained physician to perform the procedure, and cannot be done extensively in many parts of the world. Therefore, alternatives to screening to effectively prevent CRC are a great unmet need.
What Are Alternatives to Screening for Colon Cancer Prevention?
Following healthy lifestyle habits, including maintaining a healthy weight, maintaining physical activity, and giving up tobacco, can reduce the risk of CRC in everyone. These habits also help prevent other chronic diseases.
In addition to lifestyle, chemoprevention – the use of drugs to inhibit, delay, or intercept and reverse cancer formation – holds great promise. The ideal chemopreventive agent, or combination of agents, requires the benefits to outweigh the risks, especially since effective prevention is likely to require long-term use. Many different drugs have been proposed and studied over the past few decades.
The study suggests that aspirin can help prevent colon cancer
Published in an article in the journal IntestinesThe researchers conducted a systematic review and analyzed data from 80 meta-analyzes or systematic reviews of intervention and observational studies published between 1980 and 2019. In doing so, they looked at the use of drugs, vitamins, dietary supplements, and dietary factors to prevent CRC in those at moderate risk.
The authors found that regular use of aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin) or naproxen (Aleve), magnesium, and folic acid is associated with a reduced risk of CRC. In addition, a high consumption of fiber, fruits and vegetables and dairy products seem to be associated with a reduced risk. In contrast, heavy alcohol consumption and high consumption of red or processed meat is associated with an increased incidence of CRC. There was no evidence of a protective benefit for tea, coffee, garlic, fish or soy products.
The strongest evidence of protective benefit is for aspirin, including “gold standard” randomized controlled trials showing that regular use of aspirin reduces the risk of precancerous adenomatous colon polyps, the precursor to the vast majority of CRC. The level of evidence for other protective agents, including NSAIDs, magnesium, and folic acid, is low to very low.
The limitations of this review include deviations in the study populations included, study design, dosage of the active substance or substances in the studies, and duration of exposure and follow-up time. This reflects the inherent challenges in conducting studies on preventive agents for CRC that require large numbers of participants and long-term follow-up (it takes several years for normal colon tissue to turn into a polyp and then into a CRC).
What do I tell my patients?
Despite a low level of evidence, efforts to prevent cancer through dietary interventions such as a high fiber diet and minimizing red meat intake are generally recommended because they are generally not associated with negative consequences.
However, medicated interventions generally require a higher standard of evidence as they are associated with the potential for side effects. Among the drugs proposed for chemoprevention of CRC, I believe aspirin has perhaps the strongest evidence of potential effectiveness, a conclusion shared by the review. The studies included in this systematic review prompted the US Preventive Services Task Force (USPSTF) to provide low-dose aspirin (81 milligrams per day) for the joint prevention of CRC and cardiovascular disease (CVD) for people ages 50 to 59 Recommended with a 10% 10-year risk for a CVD event. However, the USPSTF warned of possible harm from aspirin, including gastrointestinal bleeding.
I generally recommend using aspirin for CRC prevention only after a detailed discussion of its potential risks and benefits, recognizing the lack of broader population-based recommendations or conclusive data to support use in additional age groups or based on other risk factors.
Follow me on Twitter @AndyChanMD