March 16, 2009 -- Question: Are there sexual practices (multiple sexual partners, etc.) that might increase the risk of developing prostate cancer?
Answer: There's been a lot of interest in the possible role of sexually transmitted infections as a causative agent for prostate cancer. Some studies show that men that have sexually transmitted infections, such as syphilis or gonorrhea, have a higher risk of prostate cancer. And if you look at all of those studies together and sort of combine them for an average effect on risk, they show that about 50 percent higher risk is found if you have a history of sexually transmitted infections.
But those studies have been very inconsistent overall. They've often been small and subject to a lot of problems that we tend to refer to as biases. For example, if you have a sexually transmitted infection, then it's very likely that you're going to be seen by a physician, maybe a urologist. So at the time you're seen, you may also have a chance of being tested for prostate cancer. So men who are seen by a physician regularly or for a specific medical condition like a sexually transmitted infection, are more likely to be diagnosed with prostate cancer.
So we're really not sure if the association that we've seen is real or if its an artifact of the opportunity to have prostate cancer detected. One of the reasons that we think about sexually transmitted infections is because they can cause inflammation in the prostate. And we think that inflammation over a long period of time plays an important role in your risk of developing prostate cancer. There have been some studies that have looked at whether having a large number of sexual partners affects your risk of getting prostate cancer and those studies seem to show a small increase in risk.
But again, these studies have been somewhat inconsistent and they may be showing the same phenomenon as sexually transmitted infections -- men who have a large number of sexual partners may have a higher opportunity to get a sexually transmitted infection and that could bring them to the attention of a physician. So right now it's still not clear if sexual practices play an important role in your risk of developing prostate cancer.