Lead author Dr. Jonathan L. Wright, an affiliate investigator in the Hutchinson Center's Public Health Sciences Division, said circumcision could hinder infection and inflammation that may lead to this malignancy.
Wright and colleagues analyzed data from 3,399 men -- 1,754 with prostate cancer and 1,645 without.
The study, published online ahead of the print edition of the journal Cancer, found men who had been circumcised before their first sexual intercourse were 15 percent less likely than uncircumcised men to develop prostate cancer.
Men circumcised before their first sexual intercourse had a 12 percent reduced risk for developing less aggressive prostate cancer and an 18 percent reduced risk for developing more aggressive prostate cancer, the study said.
Sexually transmitted infections may lead to prostate cancer by causing chronic inflammation that creates a hospitable environment for cancer cells, but other mechanisms may also be involved, Wright said.
Circumcision may protect against sexually transmitted infections, and therefore prostate cancer, by toughening the inner foreskin and by getting rid of the moist space under the foreskin that may help pathogens survive, the study said.
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