Heart Disease Marker Now Tied to Colon Cancer
C-reactive protein links tumors, simmering irritation
TUESDAY, Feb. 3, 2004 (HealthDayNews) -- A blood chemical that predicts heart attacks and strokes also seems to foretell who is likely to develop colon cancer, new research shows.
Irritation in the intestines, such as that associated with inflammatory bowel disease (IBD), has long been known to increase a person's risk of colon and rectal cancer. The new study "puts forward the idea that low-grade inflammation could be a risk factor for colon cancer" in people without severely aggravated intestines, says study leader Dr. Thomas Erlinger, an internist and epidemiologist at Johns Hopkins Medical Institutions.
The substance, C-reactive protein (CRP), is a marker of general inflammation throughout the body. People who developed colon cancer during the study had a higher CRP count at the start than those who were free of the disease.
The study didn't find a direct connection between CRP and rectal tumors, though the number of rectal cancer cases was small. A report on the findings appears in the Feb 4 issue of the Journal of the American Medical Association.
CRP was discovered in 1930 in the blood of patients with serious pneumonia. More recently, scientists have learned that people with more of the protein in their blood are at greater risk of heart attacks, strokes and several other major illnesses.
In the latest work, Erlinger and his colleagues compared CRP levels and colorectal cancer risk in nearly 23,000 residents of Washington County, Md., participating in a long-term study of heart disease and cancer. A blood test for the protein was included in a battery of exams at the start of the project, which ran between 1989 and 2000.
By the end of the study, 131 men and women were diagnosed with colon cancer, and 41 got rectal cancer. The risk of colon cancer for people in the top quarter of initial CRP levels was about 2.5 times higher than for those in the bottom quartile.
Smokers and people with bowel diseases such as Crohn's and colitis are known to have increased odds of developing colon cancer. But even after accounting for these risk factors, the link between elevated CRP and colon tumors persisted, Erlinger says.
If colon cancer is related to inflammation, aspirin and other anti-inflammatory drugs could in theory prevent the disease. And indeed, the researchers did see some hints that people who took these medications were less likely to develop colon tumors. "They did have a lower risk but we really didn't have good data there," Erlinger says. More studies are need to address the question, he adds.
Dr. Boris Pasche, director of the cancer genetics program at Northwestern University, calls the results "an interesting first study" that should encourage further research into the health effects of simmering inflammation.
"Maybe the same people with a higher risk of cardiovascular disease also have a higher risk of colorectal cancer," says Pasche, co-author of an editorial accompanying the journal article.
But it's not yet clear that elevated CRP predicts colon cancer or simply reflects tumors that are already present but too small to generate symptoms.
Erlinger's group tried to account for this possibility, but since they had only one reading of the protein they weren't able to fully exclude it in their analysis. "If you argue that there is a relationship [between CRP and cancer] you would expect that the CRP value may increase over time prior to the diagnosis of colon cancer," Pasche says.