At first, Dr. Albanes and his colleagues found their results seemed to back up the studies from the 1980s; they discovered that men with low total cholesterol had a higher cancer risk. The trend all but disappeared when they excluded cases of cancer that were diagnosed during the first nine years of the study. (Such men may have already had cancer, but it hadn’t been diagnosed yet.)
In the second study, researchers looked at about 5,500 men ages 55 and older. Men with total cholesterol under 200 mg/dL—the range the National Heart, Lung and Blood Institute deems "desirable"—had roughly a 60% lower risk of high-grade prostate cancer, an aggressive type.
"It was a notable reduction, which is not that often seen in prostate cancer research," the lead researcher, Elizabeth Platz, ScD, a cancer epidemiologist at the Johns Hopkins Bloomberg School of Public Health, told reporters.
The decrease in risk was found only in high-grade tumors and not in less serious cases of prostate cancer—a pattern that Platz and her colleagues reported in a previous, similar study. According to Jacobs, this pattern is not uncommon in prostate-cancer studies. Obesity, for example, is associated with a higher risk of more dangerous tumors but not with prostate cancer overall, he said.
This study was inspired in part by a growing body of evidence that suggests that statins, which are cholesterol-lowering drugs such as Lipitor, may protect against high-grade prostate cancer. In the current study, however, Platz and her colleagues did not measure statin use and therefore were not able to determine whether the lower risk of high-grade prostate cancer was influenced by statins or other cholesterol-lowering methods, rather than naturally low cholesterol.
"Our next step…is to look not just at total cholesterol, but to also evaluate the relationship for high HDL cholesterol and low LDL cholesterol, and also to evaluate whether cholesterol-lowering—rather than low cholesterol as the usual state for these men—would also explain this relationship," Platz said.
More studies, including randomized controlled trials, are necessary to explain the link between cholesterol and prostate cancer, according to Platz.
Jacobs agreed, noting that the findings of the two studies raise important questions. The effect that HDL cholesterol and total cholesterol have on cancer risk are "likely to be very interesting areas for future research," he said.
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