Prospective study of Trichomonas vaginalis infection and prostate cancer incidence and mortality: Physicians' Health Study.

Background: A recent nested case-control study found that the presence of antibodies against Trichomonas vaginalis, a common nonviral sexually transmitted infection, was positively associated with subsequent incidence of prostate cancer. We confirmed these findings in an independent population and related serostatus for antibodies against T vaginalis to prostate cancer incidence and mortality.

Methods: We conducted a case-control study nested within the Physicians' Health Study that included 673 case subjects with prostate cancer and 673 individually matched control subjects who had available plasma samples. Plasma from blood samples collected at baseline was assayed for antibodies against T vaginalis with an enzyme-linked immunosorbent assay. We used conditional logistic regression to estimate the odds ratios (ORs) of incident prostate cancer, extraprostatic prostate cancer, and cancer that would ultimately progress to bony metastases or prostate cancer-specific death.

Results: Although not statistically significant, the magnitude of the association between T vaginalis-seropositive status and overall prostate cancer risk (OR = 1.23, 95% confidence interval [CI] = 0.94 to 1.61) was similar to that reported previously. Furthermore, a seropositive status was associated with statistically significantly increased risks of extraprostatic prostate cancer (OR = 2.17, 95% CI = 1.08 to 4.37) and of cancer that would ultimately progress to bony metastases or prostate cancer-specific death (OR = 2.69, 95% CI = 1.37 to 5.28).

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