A new study led by researchers from the Johns Hopkins Kimmel Cancer Center in Baltimore, MD, finds that compared to men with no such signs, men with chronic inflammation in non-cancerous prostate tissue may have nearly double the risk of developing prostate cancer.
The study also finds that the link between chronic prostate inflammation and prostate cancer may be even stronger in men with high grade cancers - those with a Gleason score between 7 and 10. The Gleason score is assessed by looking at cancer cells under a microscope: a higher grade usually means more abnormal-looking cells and the cancer is growing faster.
The researchers are keen to point out their study has found a link and not a cause - their results do not prove that chronic prostate inflammation leads to prostate cancer. And neither do they believe - in view of prostate inflammation being quite widespread - that inflammation should be used to diagnose prostate cancer.
Reporting the findings in the journal Cancer Epidemiology, Biomarkers & Prevention, the team says more research should now be done to find out what causes prostate inflammation and how such causes might lead to cancer and whether they can be prevented.
According to the American Cancer Society, prostate cancer is the second most common cancer among men in the US. About 1 in 7 men will be diagnosed with the disease during his lifetime.
'Clear link' between prostate inflammation and prostate cancer
Men showing signs of chronic inflammation had 1.78 times higher odds of having prostate cancer, regardless of whether the men had low PSA at the time of biopsy.
Co-author Elizabeth A. Platz, a professor in the Department of Epidemiology at the Johns Hopkins University Bloomberg School of Public Health and in the School of Medicine, says:
"What we've shown in this observational study is a clear association between prostate inflammation and prostate cancer, although we can't prove that inflammation is a cause of prostate cancer."
Prof. Platz and colleagues analyzed samples from men taking part in the Southwest Oncology Group's Prostate Cancer Prevention Trial. The trial compared men taking the drug finasteride with men taking placebo, to determine if the drug could prevent prostate cancer.
The team were interested in the trial's placebo group, and especially in the fact they all underwent biopsies at the end of the trial, even if there was no particular reason to do so.
This was an important feature of the study design because previous investigations into links between prostate inflammation and cancer have sampled tissue from men who underwent biopsy for a reason - for instance, if they had higher prostate specific antigen (PSA). Thus the team wanted to rule out any bias that might be introduced in this way, as Prof. Platz explains:
"Because inflammation makes PSA levels go up, men with inflammation are more likely to have higher PSA and, with a rising PSA, they're more likely to be biopsied. By doing more biopsies on these men, prostate cancer is more likely to be detected, even if inflammation is not a cause of prostate cancer."
The data from the placebo arm of the trial allowed the team to examine non-cancerous tissue samples from biopsies of 191 men with prostate cancer and 209 men without prostate cancer. They analyzed the samples for presence and amount of immune cells that indicate inflammation.
Odds were the same even when PSA levels were low
They found at least one tissue sample with signs of inflammation in 86.2% of the men with prostate cancer compared with 78.2% of the men without cancer.
The results also showed that men with at least one tissue sample showing signs of chronic inflammation had 1.78 times higher odds of having prostate cancer, and 2.24 higher odds of aggressive cancer (high-grade disease, with Gleason scores between 7 and 10).
These odds were the same even in men whose PSA levels were low at the time of their biopsies.
Co-author Angelo M. De Marzo, a professor of Pathology at Johns Hopkins' School of Medicine and associate director of cancer research pathology, says:
"We knew going into this research that inflammation in the prostate is very common in men who have biopsies because of the higher PSA levels and other indicators of prostate cancer, but we did not anticipate the high prevalence of prostate inflammation in men who didn't have an indication for biopsy."
The team is now investigating in more detail how PSA and inflammation might be connected in men with indication for a prostate biopsy. The researchers also want to look into possible links between a history of sexually transmitted diseases and prostate inflammation.
The National Institutes of Health's National Cancer Institute helped fund the study.
Meanwhile, Medical News Today has learned how MRI scans may help diagnose prostate cancer more accurately. An Australian trial suggests that using the imaging technology to guide the taking of biopsy samples significantly improves the diagnosis of life-threatening prostate cancer. The hope is using such an approach could reduce the over-diagnosis of non-life-threatening cases, and avoid the side effects of unnecessary treatment.