Does Infection Boost Prostate Cancer Risk?

A new study further supports the theory that the presence of antibodies against Trichomonas vaginalis (T. vaginalis) is associated with an increased risk of prostate cancer, researchers say. Trichomoniasis, a common STD caused by the single-celled protozoan parasite T. vaginalis, infects an estimated 174 million people worldwide each year. However, three-quarters of men who are infected do not know it.

In the new nested case-control study, Jennifer Stark of the Harvard School of Public Health and colleagues analyzed plasma samples from 673 men with prostate cancer and 673 matched control subjects. Compared with the controls, those who were T. vaginalis seropositive were more than twice as likely to develop prostate cancer that was advanced at diagnosis a decade later and nearly three times as likely to die from the cancer, noted investigators.

The researchers hypothesize that the infection may increase the risk of cancer by causing inflammation in the prostate gland. An earlier nested case-control study also found a positive association between T. vaginalis antibodies and subsequent incidence of prostate cancer, noted authors of the new study.

While further studies are needed to confirm the findings, they might point to one way to reduce the risk of prostate cancer, researchers said, because T. vaginalis is easily treatable with inexpensive antibiotics.

"This large prospective case-control study obtained further support for an association between seropositive status for antibodies against T. vaginalis and the risk of prostate cancer, with statistically significant associations for the risk of extraprostatic prostate cancer and for clinically relevant, potentially lethal prostate cancer," the authors concluded.

The full study, "Prospective Study of Trichomonas vaginalis Infection and Prostate Cancer Incidence and Mortality: Physicians' Health Study," was published in advance of the printed Journal of the National Cancer Institute (2009:doi:10.1093/jnci/djp306).

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