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Patient Perspective

Exploring New Directions in Colorectal Cancer Prevention
Carol Burke, M.D.

With nearly 130,000 new cases of colorectal cancer each year, and nearly one-third of them resulting in fatalities, researchers continue to take a long, investigative look at how to stop colorectal cancer from developing. Recently, they have been looking in a newer direction – exciting developments in medicines or natural substances that may possess the power of prevention. This type of treatment approach is called chemoprevention. Cleveland Clinic researchers are instrumental in bringing some of these new therapies to use.

Diet
Besides advancing age and inherited gene mutations, our diet, including what we do not eat, can trigger genetic abnormalities in colon cells – the precursor to cancer. We cannot control our age or inheritance, but we can change our diet. Except for a recent report (see Q&A article on page 3), for years experts have found that people eating a varied diet high in fruits, vegetables and fiber and low in fat and red meat had a decreased incidence of colon polyps and cancer.

Since food is digested and the residue stored in the colon, cancer-causing chemicals from food, such as red meat, come in contact with the colon’s cell lining and can cause genetic mutations. On the upside, some foods, such as fiber, contain cancer-fighting properties that may help maintain the normal growth and death processes of colorectal cells. These foods include fruits and vegetables, especially green leafy vegetables, cabbage, broccoli and green tea.

Aspirin and NSAIDs
The most well-investigated substances for the prevention of colorectal cancer are aspirin and its cousins, nonsteroidal anti-inflammatory medicines, or NSAIDs. Many published animal and human studies have shown that aspirin and NSAID medications taken on a continuous and regular basis decrease the risk for colorectal polyps and cancer. In at least two large questionnaire studies, both men and women benefited from aspirin use. The first large, multicenter, randomized trial to help confirm the benefit of aspirin is now under way at the Cleveland Clinic and other institutions nationwide.

Sulindac, an NSAID, decreases the number of polyps and prevents them from forming in patients with a rare, inherited colorectal disease, familial adenomatous polyposis (FAP). But because sulindac produces side effects in about 20 percent of patients, Cleveland Clinic researchers are studying an active nontoxic ingredient of sulindac, exisulind, in patients with FAP. Preliminary studies showed that exisulind melted away colon polyps, and it is now being studied for prevention of polyp formation. In addition, new NSAIDs, called COX-2 inhibitors, are being studied in patients with FAP and sporadic polyps looking for the same benefits.

Vitamins and Minerals
The B vitamin folate, in a large questionnaire analysis, was associated with a reduced incidence of colonic polyps and cancer in the general population as well as in studies in patients with ulcerative colitis. Folate maintains healthy DNA and is important in DNA repair. Folate is found in a variety of natural foods, such as dark green leafy vegetables, fruits and dried beans. It also is an additive to many processed foods, such as breakfast cereals and enriched pastas. The benefit of folate supplementation in patients with polyps is currently being studied at the Cleveland Clinic. The dose of folate required for the maximum effect is unknown, but is thought to be at least 400 mcg per day.

Calcium, which is contained in many antacids, has recently been found to reduce the number and recurrence rate of colonic polyps. A large, multicenter three-year study, in which the Cleveland Clinic participated, found that a daily dose of 1200 mg of elemental calcium achieved those benefits (see Q&A article).

Teas are being sipped as more than just a soothing beverage these days. Recently, green tea has been shown to inhibit colon cancer growth in experiments with colon cancer cells and in some rodents. The use of or amount of green tea needed for benefits in humans has not yet been evaluated. But we will certainly be hearing more about green tea in the near future and will keep you posted on what we learn.

In conclusion
Although there is currently no silver bullet for colorectal cancer prevention, we are learning more about the beneficial effects of chemoprevention. But before adding any medicine or food supplement to your diet, be sure to discuss the risks and benefits of each substance with your family doctor. The importance of a healthy lifestyle including a low fat, high fiber, fruit and vegetable diet, maintenance of proper body weight and exercise should not be underestimated and is the first step in taking control of your health.

Know Your Risk Factors and Preventive Actions
Knowing the risk factors for colorectal cancer – such as your family or personal history of colonic polyps or cancer, and chronic inflammatory conditions of the colon such as Crohn’s disease and ulcerative colitis – helps identify people who would benefit from and should be undergoing regular, complete colon examinations.

Regardless of risk factors, all people over the age of 50 years should be undergoing routine colon cancer screening. At a minimum, the screening should include annual fecal occult blood testing and a flexible sigmoidoscopy every 5 years. The benefit of the colon checks is that if polyps are detected and removed, colon cancer can be prevented, or if cancer is detected in its early stages, it is most often curable.