Common sexually transmitted infection linked to aggressive prostate cancer
MedWire News: The presence of antibodies against the common sexually transmitted infection Trichomonas vaginalis, is associated with the risk for aggressive prostate cancer, US study findings show.
Researchers conducting a case control study confirmed the association between the sexually transmitted infection and the incidence of prostate cancer, whilst also discovering a statistically significant risk for diagnosis of the cancer at an advanced stage.
“Moreover, T. vaginalis infection appears to be associated with cancer that will ultimately progress to bony metastases and prostate cancer death,” say Jennifer Stark, from the Harvard School of Public Health in Boston, Massachusetts, and colleagues.
The study included 673 men with prostate cancer diagnosed between 1980 and 2000 who were each matched to a control patient without prostate cancer. Plasma from both sets of participants was tested for the presence of antibodies against T. vaginalis.
The antibody was found in 21% of control patients and 25% of cancer patients. Seropositivity was not associated with overall risk for prostate cancer, with an odds ratio (OR) of 1.23, similar to previous reports, nor risk for high-grade prostate cancer, defined as Gleason score 7–10 (OR=1.10).
However, men with antibodies did have a significant 2.17-fold increased risk for advanced stage prostate cancer, defined as T3, T4, N1 or M1 disease, and a 2.69-fold increased risk for prostate cancer which would ultimately lead to distant metastases and death. These OR were independent of factors such as body mass index, smoking status, and age at diagnosis.
The association between T. vaginalis and the development of prostate cancer was strongest for men who were diagnosed with prostate cancer closest to blood samples being taken. Among the 39 men who were diagnosed with lethal prostate cancer within 5 years of their blood test and their controls, seropositive patients were significantly more likely to develop lethal prostate cancer than seronegative men (OR=6.4).
Both the researchers and editorialist Peter Albertsen (University of Connecticut, Farmington, USA) acknowledge that the introduction of prostate-specific antigen testing in the late 1980s may have affected this outcome, with men diagnosed before 1987 more likely to have clinically significant disease than later patients.
However, the researchers believe their findings may “elucidate one mechanism by which local prostatic inflammation could arise and lead to downstream events that influence prostate cancer development and progression.”
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009
By Sarah Guy