Study Summary

In the first, large prospective study of its kind, Danish researchers report that people with high blood levels of C-reactive protein (CRP)—a marker of inflammation and a predictor of heart disease risk —have a 30 percent greater risk of developing any cancer later in life, and were associated with the risk of developing lung and possibly colorectal cancers, compared with people with low CRP levels. Researchers also found that among people with cancer, those with high CRP levels prior to their diagnosis were 80 percent more likely to die sooner than people with cancer who did not have elevated CRP.

CRP is a protein that serves as a marker of inflammation in the body. High-sensitivity CRP testing is already performed in individuals with cardiovascular risk factors to assess future risk of heart disease. Previous smaller case-control studies have reported an association between CRP and cancer, but this is the first large study to prospectively explore this relationship for any cancer, involving more than 10,000 people.

“While future research will need to confirm our findings, our study suggests that testing patients’ C-reactive protein levels provides a more comprehensive picture of a patient’s health than we previously thought. In addition to predicting heart disease risk, this simple test could help us assess a patient’s future cancer risk and eventual cancer prognosis,” said lead author Kristine Allin, MD, a physician at Copenhagen University Hospital in Denmark.

The researchers stated it is unclear whether CRP is a marker of occult (hidden) cancers or whether chronic inflammation, characterized by high CRP levels, promotes cancer growth.

The analysis included participants from the Copenhagen City Heart Study, a large prospective study launched in 1976 to explore risk factors for heart disease. All participants had baseline CRP levels measured using the high-sensitivity CRP blood test. This analysis included 10,408 participants who entered the study between 1991 and 1994 or between 2001 and 2003.

After 16 years of total follow-up, 1,624 participants developed cancer. People with a high baseline CRP (more than 3 mg/L) had a 30 percent greater risk of developing any cancer compared with those whose CRP was less than 1 mg/L. High CRP levels were associated with lung and possibly colorectal cancer risk, but did not significantly raise breast cancer risk.

Among people diagnosed with cancer during the study period, those who had baseline CRP of more than 3 mg/L were 80 percent more likely to die sooner than those with CRP levels under 1 mg/L. Specifically, researchers reported that five years after cancer diagnosis, 40 percent of patients with elevated CRP levels were alive, compared with 70 percent of patients with low CRP levels.

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