No Association of Trichomonas vaginalis Seropositivity with Advanced Prostate Cancer Risk in the Multiethnic Cohort: A Nested Case-Control Study

SIMPLE SUMMARY: Prostate cancer is one of the most common malignancies in the United States and worldwide, with geographic variability in incidence and mortality. Despite increasing incidence of distant-stage prostate cancer, the cause is poorly understood. There is inconsistent serologic evidence that Trichomonas vaginalis, a sexually transmitted protozoan, may play a role in prostate cancer development. The aim of our study was to assess the relationship between T. vaginalis seropositivity and advanced prostate cancer risk in a nested case–control study within the Multiethnic Cohort in Hawaii and California using blood samples collected prior to cancer diagnoses. Understanding the relationship between T. vaginalis seropositivity and prostate cancer risk in this diverse cohort will inform treatment and prevention efforts and address disparities in incidence and mortality. ABSTRACT: The potential involvement of a sexually transmitted agent has been suggested to contribute to the high number of prostate cancers in the United States and worldwide. We investigated the relationship of Trichomonas vaginalis seropositivity with prostate cancer risk in a nested case–control study within the Multiethnic Cohort in Hawaii and California using blood samples collected prior to cancer diagnoses. Incident cases of advanced prostate cancer (intermediate- to high-grade based on Gleason score ≥ 7 and/or disease spread outside the prostate) were matched to controls by age, ethnicity, and the date of blood collection. T. vaginalis serostatus was measured using an ELISA detecting IgG antibodies against a recombinant T. vaginalis α-actinin protein. Seropositivity to T. vaginalis was observed in 35 of 470 (7.4%) cases and 26 of 470 (5.5%) controls (unadjusted OR = 1.47, 95% CI 0.82–2.64; adjusted OR = 1.31, 95% CI 0.67–2.53). The association was similarly not significant when cases were confined to extraprostatic tumors having regional or distant spread (n = 121) regardless of grade (unadjusted OR = 1.37, 95% CI 0.63–3.01; adjusted OR = 1.20, 95% CI 0.46–3.11). The association of T. vaginalis with prostate cancer risk did not vary by aspirin use. Our findings do not support a role for T. vaginalis in the etiology of advanced prostate cancer.