As reported by the Washington Post, September 10, 2009.

Does Infection Boost Prostate Cancer Risk?

By Rob Stein

Scientists have more evidence that a common sexually transmitted infection may increase the risk of advanced prostate cancer.

Previous research has suggested that an infection known as trichomoniasis might increase the risk for prostate cancer, which is the second most common cancer and cause of cancer death among men.

In the new study, Jennifer Stark of the Harvard School of Public Health in Boston and colleagues analyzed blood samples from 673 men with prostate cancer who participated in the Physicians' Health Study, a large, ongoing study examining a variety of health issues. Compared to 673 similar men who did not develop prostate cancer, those with the infection were more than twice as likely to develop prostate cancer that was advanced when it was diagnosed a decade later and nearly three times as likely to get a lethal case, the researchers reported in the Journal of the National Cancer Institute.

The researchers speculated that the infection may increase the prostate cancer risk by causing inflammation in the prostate gland. Trichomoniasis, which is caused by a parasite called trichomonas vaginalis, infects an estimated 174 million people around the world each year, making it the most common non-viral sexually transmitted infection. Three quarters of men who have the infection don't know it.

The researchers said more studies are needed to confirm the results. But if they hold up, it would offer one way to reduce the toll from prostate cancer. The infection is easily treated with an inexpensive antibiotic regimen.

The findings marks the second time this week researchers are reporting a link between an infection and prostate cancer. As my colleague Jennifer Huget reported on Monday, another team of scientists report evidence linking a virus known as XMRV to the malignancy.

In an editorial accompanying the study, Peter Albertsen of the University of Connecticut noted that the widespread use of PSA testing has made it more difficult to identify possible causes of prostate cancer.