Ethiopian Review

Researchers affiliated with the Physicians’ Health Study have reported that men who are seropositive for Trichomonas vaginalis are at risk for more advanced prostate cancer than men who are seronegative. The details of this study appeared early online in the Journal of the National Cancer Institute on September 8, 2009.[1]

Sexually transmitted diseases have not been linked directly to the development of prostate cancer, although there has been much speculation about the role of inflammation in prostate cancer etiology. Trichomonas is a very common sexually transmitted parasitic disease that affects 170 million men and women in the world. Trichomonas has not been included in previous studies of sexually transmitted diseases related to prostate cancer. Approximately one in five U.S. men has been exposed to Trichomonas as measured by seropositivity. Infection rates are related directly to the number of sexual partners. Men have few symptoms of the disease, but symptoms are common in women with vaginal infections due to Trichomonas.

Researchers affiliated with the Physicians’ Health Study first reported an association between plasma antibodies to Trichomonas and risk of prostate cancer in 2006 in Cancer Epidemiology Biomarkers and Prevention.[2] This analysis found that 13% of prostate cancer cases were seropositive for Trichomonas compared with 9% of controls. They reported a 43% increased incidence of prostate cancer in men who were seropositive compared with controls. This effect was stronger in men who did not take regular aspirin.

A second report, from the Prostate Cancer Prevention Trial, was published in the May 1, 2009 issue of the International Journal of Cancer.[3] This study was performed to confirm the results of the first study. This study failed to confirm the original observations; seropositivity for Trichomonas was found in 15% of both the control group and men with prostate cancer. Thus, they were unable to confirm the original observations.

The current analysis included 673 patients with prostate cancer and 673 controls without prostate cancer. Prevalence of seropositivity for Trichomonas was 21% in the control group and 25% in the prostate cancer group. The overall risk (OR) of prostate cancer was 1.23 in the seropositive group, but this was not a statistically significant difference. However, they found that men who were seropositive were twice as likely to have advanced-stage prostate cancer as controls and were at an even higher risk (OR=2.69) for death or metastatic disease from prostate cancer. These authors suggest that these data support the association between Trichomonas infection and prostate cancer.

Comments: These data are not compelling that Trichomonas vaginalis infection plays a major role in the etiology of prostate cancer in the United States. Furthermore, Trichomonas infects millions of men worldwide and is common in Asia, where prostate cancer is relatively rare; this makes Trichomonas an unlikely candidate as a major cause of prostate cancer. However, these data may provide some support for those who believe that inflammation is related to the development of prostate cancer.

Reference:

[1] Stark JR, Judson G, Alderete JF, et al. Prospective study of Trichomonas vaginalis infection and prostate cancer incidence and mortality: Physicians” Health Study. Journal of the National Cancer Institute. [early online publication]. September 8, 2009.

[2] Sutcliffe S, Giovannucci E, Alderete JF et al. Plasma antibodies against Trichomonas vaginalis and subsequent risk of prostate cancer. Cancer Epidemiology Biomarkers and Prevention. 2006;15:939-945.

[3] Sutcliffe S, Alderete JF, Till C, et al. Trichomonosis and subsequent risk of prostate cancer in the Prostate Cancer Prevention Trial. International Journal of Cancer. 2009;124:2082-2097.

- By CancerConsultants

- Bin Du