Cholesterol-lowering statin drugs reduce levels of a blood marker for prostate cancer, but it's not clear they actually lower the risk of developing the disease.

Scientists from Duke University report in the Journal of the National Cancer Institute that levels of prostate-specific antigen (PSA), a protein, dropped by an average of 4.1 percent over 16 years in 1,214 men taking statins. But they didn’t explore whether the meds actually reduced the incidence of prostate cancer.

Previous research has produced conflicting results: one 2005 study by the Veterans Administration suggested that statins lowered risk of the disease, but three analyses of their use for heart disease between 2005 and 2007 didn't show any link.

"It's obviously the unanswered question: Is this a good thing that we've lowered their PSAs, and therefore their chance of prostate cancer is lower? Or are we just masking the cancer and making it harder to detect?" study author Stephen Freedland, a Duke urologic surgeon, told Reuters. "I wish I had that answer."

Prostate cancer causes nearly 30,000 deaths annually, but PSA screening may not reduce mortality from the disease, according to the National Cancer Institute (NCI). Use of the PSA test has become controversial, as an editorial accompanying the study points out: though it doubles a man's chances of being diagnosed with the disease at some point in his life, experts say that in some cases the tumors are so slow-growing that patients are more likely to die from something else. Invasive treatments for prostate cancer may cause lasting side effects, such as impotence and incontinence.

In related news, the NCI cancelled a $120 million, 7-year trial of 35,000 men taking selenium and vitamin E supplements as possible safeguards against prostate cancer. The trial was cancelled four years in after scientists saw an unexpected increase in tumors among some of the men taking vitamin E, and a rise in adult-onset diabetes in some of those taking selenium.

"If indeed this worked, it was going to be quite a wonderful thing, because it could lead to risk reduction through relatively cheap stuff that could be bought over the counter," says Richard Macchia, a urologist who was the trial's local principal investigator at SUNY Downstate University Hospital and Kings County Hospital Center in Brooklyn, New York. But by pulling the plug on the trial, he says, "They did the right thing, and it’s the safest thing to do."

(Image of prostate cancer awareness ribbon by iStockphoto/Joe Belanger)