Primary prevention

Several interventions have been reported to reduce the risk of colorectal cancer.

Aspirin

Multiple studies have reported that aspirin use is associated with a lower risk of colorectal cancer.[79][80][81][82]​​​ One cohort study reported greater absolute reduction in colorectal cancer risk among individuals with less healthy lifestyles.[80] One pooled analysis of two large US cohort studies found that aspirin use reduced the risk of colorectal cancer if initiated before age 70 years and continued beyond age 70, but initiation at older age did not reduce the risk.[82]

Guidelines differ with regard to aspirin as a preventative drug for colorectal cancer. The US Preventive Services Task Force has published a systematic review and guidance on the use of aspirin to prevent cardiovascular disease and colorectal cancer. Aspirin is no longer recommended as a preventative treatment for colorectal cancer, because of a lack of high-quality evidence that it reduces colorectal cancer incidence or mortality.​[39][83]

The American College of Gastroenterologists recommends low-dose aspirin in adults ages 50-69 years with a cardiovascular disease risk of ≥10% over the next 10 years, who are not an increased risk for bleeding, and are willing to take aspirin for at least 10 years to reduce the risk of colorectal cancer.[84]

Research regarding the clinical utility of aspirin for the primary prevention of colorectal cancer in average- and increased-risk patient populations is ongoing.[82][85][86][87]​​[88]

Aspirin may help prevent colorectal cancer in patients with Lynch syndrome. Guidelines recommend daily aspirin (taken for more than 2 years) to prevent colorectal cancer in people with Lynch syndrome (hereditary nonpolyposis colorectal cancer).[39][89][90][91]​​

Nonsteroidal anti-inflammatory drugs (NSAIDs)

One systematic review, including over one million people in the analysis, found that regular use of non-aspirin NSAIDs reduced colorectal cancer in people ages 40 years and older.[92] Significant protective effects were found for women, high doses, distal colon cancer, and white people.[92]​ Non-aspirin NSAIDs are not recommended for the prevention of colorectal neoplasias.[93]​ Randomized controlled clinical trials have shown that cyclooxygenase (COX-2) inhibitors reduce the adenoma recurrence rate, which may have implications for subsequent cancer risk.[94]

Diet/dietary supplements

Healthy plant-based diets rich in whole grains, fruits, and vegetables may reduce the incidence of colorectal cancer, especially KRAS wild-type colorectal cancer. Diets rich in refined grains and sugar should be avoided.[95][96][97]​​​​

One dose response meta-analysis found that vitamin B2 intake is inversely associated with colorectal cancer risk.[98]​ One systematic review and meta-analysis reported that high vitamin B9 intake may be protective against colon cancer, especially in individuals who consume moderate to high alcohol; further trials are needed to confirm this finding.[99]​ The American Gastroenterological Association (AGA) advises against the use of vitamin B9 to prevent colorectal neoplasias.[93]

Consumption of fish and long-chain n-3 polyunsaturated fatty acids at levels recommended by the World Health Organization has been associated with a reduced risk of colorectal cancer.[100][101]

There is a controversy as to whether calcium and vitamin D supplementation prevents colorectal cancer.[102][103][104][105][106]​​​​​ Natural sources, such as dairy products, may be beneficial over supplements.[103]​ One systematic review and meta-analysis suggests that higher dietary intake of vitamin D may be effective in reducing colorectal cancer risk.[104]​ The AGA advises clinicians against prescribing calcium or vitamin D (alone or in combination) to prevent colorectal neoplasias.[93]

As low levels of vitamin D have been associated with increased cancer risk, the National Comprehensive Cancer Network advises supplementation in individuals who are deficient in this vitamin may be beneficial. It also recommends that in general, nutrients should be obtained from natural food sources rather than solely from dietary supplements.[39]

Colonoscopic polypectomy

Colonoscopic removal of adenomatous polyps prevents deaths from colorectal cancer.[107] 

Smoking cessation

Long-term cigarette smoking is associated with increased colorectal cancer incidence and mortality.[7][45]​ R​isk reduction is seen with early smoking cessation; smoking cessation counseling is strongly recommended.[39][40][41]

Alcohol reduction

Moderate to heavy alcohol consumption has been associated with increased colorectal cancer risk, suggesting that reduction in alcohol intake may be beneficial in this patient group.[39][43][46]​ One meta-analysis of 61 independent studies (27 cohort and 34 case-control studies) examined the association of alcohol intake (light, moderate, or high) and colorectal cancer risk. Compared with nondrinkers or occasional drinkers, moderate drinking (2-3 drinks/day, equivalent to 12.6 to 49.9 grams of ethanol/day) and heavy drinking (≥4 drinks/day, equivalent to ≥50 grams of ethanol/day) were associated with increased risk of colorectal cancer, of 21% and 52%, respectively.[42]

Reduction in consumption of red and processed meat

As high intake of red and processed meat is associated with an increased risk of colorectal cancer, a reduction in intake may reduce the risk of developing colorectal cancer.[31][32]​[33]

Secondary prevention

Aspirin

An improvement in colorectal cancer-specific survival and overall survival has been noted with aspirin when used for secondary prevention.[39]​ One systematic review found that low dose aspirin reduced the risk of recurrent adenomas in patients with a previous history of colorectal cancer or adenomas.[406] The effect on advanced adenomas was inconclusive. 

Regular aspirin use post-diagnosis is associated with longer survival among patients with mutated-PIK3CA colorectal cancer.[407]

Nonsteroidal anti-inflammatory drugs (NSAIDs)

One systematic review found that NSAIDs are the most effective agents for the prevention of advanced metachronous neoplasia in patients with previous colorectal cancer.[408]

Results from a meta-analysis indicate that COX-2 inhibitors may be effective at reducing the risk of recurrent adenomas in patients with a previous history of colorectal cancer or adenomas.[406] However, a trend toward increased risk of recurrent adenomas was observed 2 years after withdrawal of the COX-2 inhibitor.

There is some evidence to suggest that NSAIDs may improve survival in people with KRAS wild-type tumors.[409]

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