At any given moment, numerous researchers around the world are conducting scientific studies probing how prostate cancer develops, what causes it or how the disease can be treated.
Now, a growing number of experts in the scientific community are pushing for some of those studies to examine a potentially important link between prostate cancer and cholesterol-lowering drugs known as statins. A new study by Canadian researchers, published in the September issue of the journal European Urology, is adding to those calls.
Researchers at St. Michael's Hospital in Toronto found that a statin called rosuvastatin seemed to suppress growth of human prostate cancer cells that had been transplanted into mice.
"I think it is exciting," said Xiao-Yan Wen, a staff scientist at the hospital and lead author of the study. "I think it's … very convincing experimental evidence."
The study adds to mounting evidence suggesting statins may play a role in inhibiting prostate cancer development.
In June, a study published in the journal Cancer found that more than 1,300 men who took statins when undergoing surgery to treat prostate cancer had a 30 per cent lower risk of recurrence than those who didn't take the drugs.
Another study by researchers at the Mayo Clinic and presented last year at a meeting of the American Urological Association found men who took statins were less likely to develop prostate cancer compared with men who weren't on those drugs.
The findings may sound promising.
But the problem is many of the studies have major weaknesses that make it difficult to tell with any certainty whether statins truly play a role in reducing prostate cancer risk. Dr. Wen's study, for instance, didn't involve humans.
And many other studies that found a connection between statins and prostate cancer risk were "retrospective" in design. In other words, the studies were conducted by taking previously collected medical data to look for anomalies or trends.
While this type of study has proven to be a valuable tool for researchers, it also comes with some baggage. For instance, researchers may not be able to take into account how lifestyle factors of those they're studying could have influenced their cancer risk. It's possible that men taking statins also exercised more, smoked less and had a better diet than those not on statins. The fear is the researchers may be wrongly assuming that statins helped drive down the cancer risk instead of another factor.
That's why more researchers are calling for large randomized-controlled trials to determine the relationship between cholesterol-lowering drugs and prostate cancer. In this instance, a randomized-controlled trial could follow two groups of men with similar characteristics for a long period of time. One group would take statins, the other would not and after 10 or 15 years, researchers would be able to see what difference it made on their risk of developing prostate cancer, if any.Anthony D'Amico, professor of radiation oncology at Harvard University's medical school and chief of genitourinary radiation oncology at the Brigham and Women's Hospital and Dana-Farber Cancer Institute, wrote an editorial in the June issue of the Journal of Clinical Oncology arguing for stronger studies. Dr. D'Amico wrote that "a definitive prospective randomized study is lacking," to determine whether statins reduce prostate cancer recurrence.Any future studies would also have to take into consideration the side effects and other problems associated with statins. Research has shown statins, including drugs sold under the brand name Lipitor and Crestor, may increase the risk of liver, kidney or cataract problems. Some people may also develop muscle pain or more serious muscle-related conditions.
Susan Langlois, director of research programs at Prostate Cancer Canada, said her advocacy group has not received funding proposals for studies looking at prostate cancer and cholesterol-lowering drugs. She said the issue isn't high on the association's radar.
"Right now, it's not something that is a priority for us to look at," she said, adding that it is probably worthwhile if researchers embark on more animal studies to see if statins can help reduce the risk of prostate cancer.
"Anything that looks like it could reduce risk without major side effects would be very important for the community," Ms. Langlois said.