Avoiding risk factors, increasing protective factors may help prevent cancer.
Avoiding risk factors, such as smoking, being overweight, and lack of exercise; and increasing protective factors, such as quitting smoking and exercising, may help prevent some cancers. You can talk to your doctor or other health care professional about how to reduce your cancer risk.
The following factors increase the risk of colorectal cancer:
Age
The risk of colorectal cancer increases after age 50. Most colorectal cancers are diagnosed after age 50.
Family history of colorectal cancer
A parent, sibling, or child with colorectal cancer increases the individual’s risk of colorectal cancer about 1-fold.
Personal history
Individuals with the following personal histories have an increased risk of colorectal cancer:
Genetic risk
Some genetic disorders, familial adenomatous polyposis (FAP) or hereditary nonpolyposis colorectal cancer (HNPCC or Lynch syndrome) are associated with specific genetic alterations that in turn cause an increased risk of colorectal cancer.
Alcohol
Consumption of three or more alcoholic beverages per day increases the risk of colorectal cancer. Also drinking alcohol may contribute to the risk of colorectal macroadenomas (benign tumors).
Smoking
Smoking increases the incidence of and death from colorectal cancer.
Smoking also increases the risk of colorectal adenomas. The risk of recurrence after colonoscopic removal of adenomas is higher in smokers.
Race
African Americans have a higher risk of colorectal cancer incidence and death compared with other races.
Obesity
Obesity increases the incidence of and death from colorectal cancer.
The following protective factors may reduce the risk of colorectal cancer:
Physical activity.
A lifestyle that includes regular physical activity may reduce the risk of colorectal cancer.
Aspirin
Studies have shown that taking aspirin can reduce the risk of colorectal cancer and the risk of death. This benefit, however, does not begin to show up until 10 to 20 years after the patient takes the drug.
Aspirin taken in small doses (≤100 mg) daily or every other day may increase the risk of stroke and gastrointestinal bleeding. The risk is higher in the elderly, in men, and in those at high risk of bleeding.
Combined hormone replacement therapy:
Studies have shown that combined hormone replacement therapy (HRT), which includes estrogen and progesterone, reduces the risk of invasive colorectal cancer in postmenopausal women.
However, women with colorectal cancer who receive combination hormone replacement therapy tend to have advanced disease at the time of diagnosis, and the prognosis for advanced colorectal cancer is poor, and thus mortality from colorectal cancer is not reduced.
Combined hormone replacement therapy may increase the risk of:
Polyp removal
Most colorectal polyps are adenomas and are considered the precancerous stage of colorectal cancer. The ability to detect and remove colorectal polyps larger than 1 cm (pea size) at an early stage may reduce the risk of colorectal cancer. It is not clear whether the removal of small colorectal polyps reduces the risk of colorectal cancer.
Polyps removed by colonoscopy or sigmoidoscopy may cause bleeding from rupture of the colon wall.
Colonic polyps. Some polyps have a tip and some do not. The inset shows a photo of a polyp with a tip.
It is not clear whether the following factors affect the risk of colorectal cancer:
Non-steroidal anti-inflammatory drugs (NSAIDs) other than aspirin
It is not clear whether NSAIDs or NSAIDs (such as sulforaphane, celecoxib, naproxen, and ibuprofen) can reduce the risk of colorectal cancer.
Studies have shown that taking the NSAID celecoxib reduces the risk of recurrence after removal of colorectal adenomas (benign tumors). It is not clear whether this reduces the risk of colorectal cancer.
Taking sulforaphane or celecoxib has been shown to reduce the number and size of polyps that form in the colon and rectum in people who have familial adenomatous polyps (FAP). It is not clear if this reduces the risk of colorectal cancer.
Side effects of nonsteroidal anti-inflammatory drugs:
Calcium
It is not known whether taking calcium supplements is effective in preventing colorectal cancer.
Diet
Whether reducing fat and meat intake and increasing consumption of dietary fiber, fruits and vegetables can prevent colorectal cancer is also unclear.
Some studies have shown that a diet high in fat, protein, calories, and meat increases the risk of colorectal cancer, while some studies have found the opposite.
The following factors do not affect the risk of colorectal cancer:
Estrogen replacement therapy
Estrogen replacement therapy does not reduce the risk of incidence and death from invasive colorectal cancer.
Statin drugs
Studies show that taking statins (cholesterol-lowering drugs) does not increase or decrease the risk of colorectal cancer.
Cancer prevention clinical trials are designed to look at ways to prevent cancer.
Cancer prevention clinical trials are studies that look at ways to reduce the risk of developing certain cancers. Some cancer prevention trials are studies that look at people at high risk for tumors. Some are studies of existing cases of disease to prevent tumor recurrence and reoccurrence. Still other trials are studies in which healthy human volunteers are selected.
The purpose of cancer prevention clinical trials is to determine whether various measures taken are effective in preventing cancer. These include increasing exercise, quitting smoking, taking certain medicines or vitamins or minerals, or other food supplements.
New approaches to preventing colorectal cancer are being tested in clinical trials.
Information about NCI-supported clinical trials can be found on the NCI’s Clinical Trials Search page. Clinical trials supported by other organizations can be found on the ClinicalTrials.gov website.