Increased levels of two markers of inflammation, interleukin-6 (IL-6) and C-reactive protein (CRP), are significantly associated with prostate cancer incidence and mortality almost a decade prior to diagnosis, say researchers at the Harvard School of Public Health.
They also found that elevated CRP in these men was associated with a two-fold increased risk of developing fatal prostate cancer, compared to men with the lowest levels of the protein.
"The results of this study provide further evidence that inflammation is involved in development and progression of prostate cancer," said the study's lead author, Jennifer Rider Stark, a graduate student in epidemiology.
Stark said that IL-6 and CRP were more strongly associated with prostate cancer risk and death from prostate cancer in normal weight men. Because IL-6 is secreted from adipose (fat) tissue, levels of the cytokine are naturally higher in overweight or obese men. "It is possible that high levels of IL-6 and CRP in men with a healthy body weight may be more indicative of a pro-inflammatory environment in the prostate," she said.
Some studies have already shown that high levels of IL-6 and CRP can be associated with a poor prognosis in prostate cancer patients, but this is one of only a few studies to examine whether these markers can predict risk before symptoms develop and cancer is diagnosed.
The findings come from a prospective study nested within the Physician's Health Study, and included 516 men who later developed prostate cancer and 516 matched controls who did not. The researchers examined blood taken from each participant early in the study - a median of 9.4 years before prostate cancer was diagnosed in the cases. Levels of IL-6 and CRP were compared among men who did and did not go on to develop cancer. Long-term follow-up of the cases also allowed the researchers to assess the effect of these markers on prostate cancer mortality.
They found that high levels of CRP in the blood was associated with a higher incidence of prostate cancer development among all patients and associated with a two-fold increased risk of developing lethal prostate cancer. IL-6 levels were not associated with prostate cancer risk overall. But when they separated out men by body mass index, those who had a healthy weight and high IL-6 in their blood had a 40 percent higher risk of developing prostate cancer.
Researchers suspect that abnormal amounts of IL-6 and CRP are markers of biological processes involved in development of a number of diseases, including cancer. IL-6 is secreted by immune cells in response to infection or trauma, and it, in turn, stimulates synthesis of CRP in the liver, which is believed to play a role in response to infections and cellular damage control. CRP has been found to be a marker of cardiovascular disease, diabetes and colon cancer, but its use as a cardiology screening test has been controversial.
Stark noted that the predictive power of these two markers for determining prostate cancer risk and mortality needs to be confirmed in other prospective studies. She added, "Understanding the role of inflammation in prostate cancer is important because inflammatory pathways could potentially be targeted for prevention and treatment."
Materials provided by American Association For Cancer Research. Note: Content may be edited for style and length.
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