A clinical study following 2,447 men aged between 40 and 79 for more than 15 years found those taking statins were less likely to develop prostate cancer, compared with men who did not take the drugs.
Just 7 per cent of men on statins were diagnosed with prostate cancer, with non-statin users three times more likely to develop the disease, Mayo Clinic researchers reported at the American Urological Association meeting in Chicago.
Their long-term analysis also found men on statins were less likely to suffer benign prostate enlargement or erectile dysfunction.
"In recent years, it has been suggested that statin medications may prevent development of cancer," said Rodney Breau of the Mayo Clinic.
"However, until now, there has been limited evidence to support this theory.
"Our research provides evidence that statin use is associated with a threefold reduced risk of being diagnosed with prostate cancer."
But the scientists said their findings were still preliminary and further randomised clinical studies would be needed to prove that statins did actually prevent cancer.
The research will be read with interest by clinicians and investors, ahead of results from another key clinical trial with GlaxoSmithKline Plc's Avodart, which the British company is hoping to establish as the first medicine for prostate enlargement to also prevent cancer.
Details of the Avodart trial will be unveiled at the same meeting in Chicago this week.
Statin drugs include Pfizer Inc's Lipitor, the world's top-selling medicine, and AstraZeneca Plc's Crestor, as well as a number of cheap generics.
Statins are currently used to lower cholesterol, thereby reducing the risk of heart attack and stroke in high-risk patients.
In the laboratory setting, researchers have observed that they also prevent cancer cells from dividing and, in fact, may cause some cancer cells to die.
