To Your Health

What is CRP and what is the connection to cancer?

Q. I consider myself healthier than most men, but at my last physical exam my physician included a CRP test among other routine blood tests, and it came back elevated. He seemed very concerned especially when he found out two of my aunts had colon cancer. What is CRP and what is the connection to cancer?

A. Your physician is wise to be concerned. C-Reactive Protein is a protein made exclusively in the liver and secreted during an inflammatory response. Normally it is secreted in response to a short-term trauma such as an infection and the levels rise and fall back to normal within a week or so. Low-grade, long-term inflammation may also raise CRP, indicating that the immune system is mounting a defense that becomes damaging to otherwise healthy tissues. One theory relates chronic infections to significantly elevated risk of heart disease and more recently to colon cancer.

The value of CRP as an inflammatory marker has been known since 1930, but development of a new "highly sensitive" CRP test, along with additional research connecting elevated CRP to heart disease, stoke, and colon cancer, enhances the importance of the test. The importance of managing inflammation is hard to overestimate (see "To Your Health," June 20, 2003).

A chronic inflammation indicated by elevated CRP results in significant damage to the arteries. Research indicates that plaques in blood vessels only pose a danger when the blood vessels are also affected by inflammation, which weakens them. The inflammation also makes the plaques more likely to cause a clot, which may block a blood vessel.

CRP may be a better predictor of heart attack risk than high cholesterol, since about half the men who die as a result of their first heart attack have a normal cholesterol level. Paul Ridker, M.D., estimates that 25 million to 35 million Americans have total cholesterol within the normal range but higher-than-average inflammation markers, which significantly raises their risk of heart disease. Both the Physicians' Health Study, involving 22,000 men, and the Women's Health Study, which involved 39,000 postmenopausal women, suggest that people with the highest levels of CRP have a much higher risk of heart attack or stroke compared to those with the lowest levels.

In addition to this concern about heart disease and stroke, researchers at the Johns Hopkins Bloomberg School of Public Health, after examining the medical records of 23,000 people, reported a potential link between elevated CRP and colon cancer. Those with the highest levels of CRP had more than double the risk of developing colon cancer compared with subjects with the lowest CRP levels.

Restricting fat of all sorts may actually promote inflammation. Diets low in omega-3 fatty acid and high in omega-6 oils and hydrogenated fats containing trans-fatty acids – the typical American diet – create an imbalance of pro-inflammatory and anti-inflammatory fats. An increased intake of omega-3 fatty acids has been associated with lower levels of CRP.

With this "heads up," your physician will likely now carefully seek to rule out type 2 diabetes, elevated blood pressure, and chronic infection, as well as cardiovascular and colon problems, in order to find the root cause of elevated CRP.

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