Early Warning? Inflammatory protein is tied to colon cancer risk

C-reactive protein (CRP), a compound that studies have associated with heart disease, may also signal susceptibility to colon cancer, researchers report in the Feb. 4 Journal of the American Medical Association. The study is the first to link elevated blood concentrations of CRP with cancer risk in a large group of people.

While CRP’s role in the body is poorly understood, it consistently shows up in inflammation, which has been linked with heart disease.

Inflammation’s role in cancer isn’t as well established, but researchers have found that various organs are at extra risk of cancer when they’re chronically inflamed. For instance, a colon beset by an inflammatory bowel disease is more likely to develop tumors than a normal colon is.

To investigate whether there’s a link between CRP and cancer, Thomas P. Erlinger of Johns Hopkins Medical Institutions in Baltimore and his colleagues identified 172 adults who had developed colorectal cancer between 1989 and 2000 while participating in a large health study. All had given blood samples at the study’s start, when they were free of cancer, and had periodically filled out questionnaires on their health during the 11 years of the study.

The researchers selected as controls 342 people without cancer who had participated in the same study and who matched the cancer patients in age, gender, and race. In their data analysis, the scientists also accounted for participants’ smoking habits, body weight, and use of hormones and anti-inflammatory drugs.

The blood samples revealed that the people with colon cancer had an average CRP concentration of 2.69 milligrams per liter at the start of the study, whereas the controls averaged only 1.97 mg/l. No CRP link to rectal cancer emerged.

The association between elevated CRP and colon cancer held up even when the researchers eliminated results from people who were diagnosed with the cancer within 2 years of their initial blood test and so might have had undetected cancer at the start of the study.

The excess risk attributable to higher CRP remained significant even after accounting for weight differences among the participants, says Erlinger.

The findings concur with previous reports that aspirin and other anti-inflammatory drugs can lower colon cancer risk, Boris Pasche of Northwestern University School of Medicine in Chicago and Charles N. Serhan of Harvard Medical School in Boston note in the same journal issue.

Erlinger and his team present “really good work,” says Lisa Coussens, a cancer biologist at the University of California, San Francisco. The study reinforces the link between inflammation and cancer, she says.

The new findings might spur researchers to investigate links between CRP and other cancers and to sort out whether CRP is a contributor to inflammation or simply a bystander, Coussens says.