03/12/2012 12:10 pm ET

Circumcision May Reduce Prostate Cancer Risk, Study Shows

Men who undergo circumcision may have a decreased risk of developing prostate cancer, according to a new study. The finding suggests that the removal of the foreskin before a man first has sex may help protect against the disease -- the most common cancer in men in the United States.

In the paper, published online Monday in the journal Cancer, researchers looked at data from more than 1,700 men with prostate cancer and more than 1,640 without, collected in two separate studies. The men answered questions about their family and medical history and sexual experience. They also indicated whether or not they had been circumcised and, if so, at what age.

Overall, the researchers found that men who had been circumcised before having sex for the first time had a 15 percent lower risk of developing prostate cancer.

"For a long time -- say, 20-plus years -- it has been recognized that certain factors related to sexual behaviors are also related to increased risk of prostate cancer," said Dr. Janet Stanford, a member of the public health sciences division at the Fred Hutchinson Cancer Research Center and one of the study’s authors.

She explained that exposure to sexually transmitted infection may lead to infectious agents getting into the prostate and stimulating a chronic, inflammatory response. That response could create a hospitable environment for cancer cells. (Prostate cancer is caused by changes in the DNA of prostate cells.)

The study's authors write that "infection and inflammation in the prostate may be important mechanisms that enhance the risk of subsequent development in prostate cancer in some men."

They cite “growing evidence” that highlights the role sexually transmitted infections may play in cancer development, as well as data that suggest circumcision reduces the risk of developing STIs.

Thus the new study, they write, presents a "biologically plausible mechanism" for circumcision reducing the risk of prostate cancer.

"It's very innovative and thought-provoking, but this kind of epidemiological research -- how A affects B, and B affects C -- is very difficult to do and makes it very difficult to account for confounding variables," said Dr. Andrew Freedman, vice chair of pediatric surgical services at Cedars-Sinai Medical center and a member of the American Academy of Pediatrics’ task force on circumcision.

"This was a large study, and a large study will often find differences that are statically significant, but clinically un-important," said Dr. Robert Van Howe, a clinical professor in the department of pediatrics and human development at Michigan State University. In a 2007 letter to the editor of the British Journal of Urology, Van Howe -- who has been a vocal opponent of circumcision -- said the concept of using circumcision to reduce prostate cancer risk has no biological foundation.

In recent years, circumcision has become an increasingly contentious issue among medical professionals, parents and even lawmakers.

The American Academy of Pediatrics last issued guidelines in 1999, saying that existing evidence provides potential medical benefits to newborn male circumcision, but not enough to recommend it routinely. The Centers for Disease Control and Prevention's recommendations are still in development.

Recent CDC estimates found that circumcision has declined in the U.S. The rate of in-hospital procedures dropped from nearly 63 percent in 1999 to approximately 57 percent in 2008. It suggested that Medicaid coverage of circumcision may be one of the many factors influencing rates.

Despite this broader context, Stanford told The Huffington Post that she and her co-authors were most focused on attempting to understand how prostate cancer develops. She called it a very focused paper that may help get at the question of what role, if any, infection plays in prostate cancer development and also in how the underlying pathways and mechanisms may work.

The authors of the new study joined with outside experts in saying that the findings are preliminary and that further research is required.

"It's a great first shot across the bow," Freedman said. "But it's not really a game changer."