Men whose benign prostate biopsy cores showed signs of chronic inflammation had more than twice the odds of high-grade prostate cancer, investigators reported online April 18 in Cancer Epidemiology, Biomarkers & Prevention.
The association existed even when prostate-specific antigen was low (less than 2 ng/mL at biopsy), suggesting that the results were not due to detection bias, said Dr. Bora Gurel of Johns Hopkins University, Baltimore, and his associates.
The nested case-control study included 191 patients with biopsy-proven prostate cancer and 209 cancer-free patients from the placebo arm of the Prostate Cancer Prevention Trial. To measure the presence and extent of inflammation, a pathologist who was blinded to case-control status examined stained tissue sections from benign areas of prostate biopsy cores. The presence of any inflammatory cells, both acute inflammatory cells and chronic inflammatory cells (cells with an appearance consistent with that of lymphocytes and macrophages) in the benign tissue for each biopsy core on each slide, were noted.
Signs of inflammation were found in at least one biopsy core in 78.2% of controls, 86.2% of cases overall, and 88.4% of high-grade cases. Most of the signs of inflammation in both controls and cases reflected chronic inflammation.
Men who had at least one biopsy core with inflammation had greater odds of a prostate cancer diagnosis (odds ratio, 1.78; 95% confidence interval, 1.04–3.06) than men who had zero cores with inflammation, and even greater odds of a high-grade diagnosis (OR, 2.24; 95% CI, 1.06-4.71), the researchers reported (Cancer Epidemiol. Biomarkers Prev. 2014 April 18 [doi: 10.1158/1055-9965.EPI-13-1126]).
But it was unclear if inflammation preceded cancer onset, because the biopsy cores were obtained to evaluate patients for prostate cancer, the investigators said.
The finding that inflammation, primarily chronic, in benign prostate tissue is associated with an increased odds of prostate cancer, and high-grade prostate cancer in particular, will inform the etiology of this disease, the investigators concluded.
"Identifying those men at highest risk of developing aggressive disease is the first step in being able to prevent lethal prostate cancer," they said. "Rather than targeting interventions to all healthy men, which may result in unintended harms, if causal, the findings from our work may allow preventive interventions to be targeted to those men who would benefit the most," they wrote.
The National Cancer Institute funded the study. The authors disclosed no relevant financial conflicts of interest.