Infections, Race, and Prostate Cancer
You can’t “catch” prostate cancer like a cold. So why is epidemiologist Elizabeth A. Platz, Sc.D., so interested in the fate of men who have sexually transmitted diseases and other infections? Because these infections cause chronic infection in the prostate, and this, in turn, causes chronic inflammation — which can lead to prostate cancer.
In a collaboration with a scientist from the Department of Defense, which has a large medical and blood specimen repository, Siobhan Sutcliffe, Ph.D., the postdoctoral fellow leading the project, and Platz, her mentor, will be studying men who have infections, including sexually transmitted infections, to see if there is any short- or long-term change in PSA.
This study is timely and relevant, the investigators say, because chronic inflammation and cell damage are believed to contribute to the development of prostate cancer precursor lesions — and because young men with elevated PSA concentrations have been found to have a higher risk of prostate cancer later in life. Because of this, it is crucial to address the mechanisms of early prostate cancer formation and PSA elevation, and determine the extent to which infections play a role.
In another study, led by German scientist Sabine Rohrmann, who was a postdoctoral fellow working with Platz, Platz and colleagues have been looking at hormonal differences and race. “One of our long-standing research interests is identifying factors that explain the notably higher risk of prostate cancer in African American men,” Platz says. Several years ago, using data from the Health Professionals Follow-Up Study, Platz found that black men had an 80 percent higher incidence of prostate cancer.
This work was published in the Journal of the National Cancer Institute. Although some early studies had shown higher levels of blood testosterone in black men than in white men, Platz felt that these studies were not as complete as they could be, and that not enough men had been studied. In this recent study, published in the Journal of Clinical Endocrinology & Metabolism, Platz and colleagues looked at blood levels of the hormones testosterone, estradiol, and a protein called sex hormone binding globulin in more than 1,400 men. The men were participants in the Third National Health and Nutrition Examination Survey. “We took into account factors that may influence hormone concentrations, including age, body fat, physical activity, and whether or not the men drank alcohol or smoked,” Platz says.
The results turned up something new: The researchers did not find very significant differences in testosterone levels between black and white men. But black men had more estradiol. More studies are needed, Platz says, looking at estradiol as well as testosterone, in relation to prostate cancer and other diseases where race clearly plays a role.