Prostate Cancer and Association With Plasma Cholesterol
Prostate cancer patients who had lower levels of cholesterol in their blood had a significantly reduced chance of developing more aggressive forms of the disease, compared to patients with higher cholesterol readings.
These findings may help explain the earlier discovery, reported by the same team of researchers at the AACR annual meeting in 2005, that men who used statin drugs experienced half the risk of developing advanced prostate cancer.
"Statin drugs reduce cholesterol in the blood, but they also influence a number of different pathways," said the study's lead researcher, Elizabeth Platz, ScD, MPH, an associate professor in the Department of Epidemiology at Johns Hopkins Bloomberg School of Public Health. "This study suggests that the ability of statins to lower cholesterol may be important to prostate carcinogenesis, but we are continuing to examine other pathways with which statin drugs interact, such as reduction of inflammation."
The researchers looked at cholesterol levels first because cholesterol affects cell signaling and survival. Some scientists theorize that a large quantity of cholesterol in the blood could stimulate the survival of abnormal prostate cells.
They studied blood drawn from 698 men before they were diagnosed with prostate cancer and matched it to blood taken from 698 men who had not been diagnosed with the disease. All of the men participated in Harvard University's Health Professionals Follow-up Study, a group of 18,018 participants who provided a blood sample between 1993 and 1995.
They found that mean cholesterol levels did not differ between the men with prostate cancer and the control participants, suggesting that cholesterol was not involved in the initial development of prostate cancer, Platz said.
But when comparing men who had the lowest quartile of serum cholesterol to men who had the highest, they found that prostate cancer patients with lower cholesterol had the lowest risk of developing a more worrisome form of the disease. They specifically found that the risk of being diagnosed with high-grade or advanced cancer was reduced by 40 percent and 50 percent, respectively.
Platz says it is not clear at what levels serum cholesterol may stimulate the abnormal growth seen in cancer development. "The findings suggest either that high cholesterol may push existing prostate cancer to become aggressive, or, alternatively, very low levels of cholesterol may provide protection against development of an aggressive cancer," she said. "We just don't know which it is at this point."
She also said that because the findings come from an observational study, not a trial, it is impossible to conclude that men can lower their risk of developing an aggressive form of prostate cancer by reducing their intake of saturated fat, the type of fat that increases serum cholesterol, which some studies have linked to an increased risk of advanced prostate cancer.
"It is too soon to say that such measures would be specifically beneficial to lowering such a risk, but for good health in general, it is prudent to consume a diet that contains healthful fats that do not increase serum cholesterol," she said.