"We show that men in upper range of the normal distribution of serum calcium subsequently have an almost three-fold increased risk for fatal prostate cancer," said Gary G. Schwartz, Ph.D., associate professor of cancer biology and of epidemiology and prevention at Wake Forest, a part of Wake Forest University Baptist Medical Center. Such excess calcium can be lowered, he said.
The research appears in the September issue of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
Co-author Halcyon G. Skinner of the School of Medicine and Public Health at the University of Wisconsin stressed there is "little relationship between calcium in the diet and calcium in serum. So men needn't be concerned about reducing their ordinary dietary intakes of calcium."
Schwartz and Skinner analyzed the results of 2,814 men who participated in the National Health and Nutrition Examination Survey (NHANES-1). Measurement of the amount of calcium in the bloodstreams was determined an average of 9.9 years before prostate cancer was diagnosed.
The researchers focused on the 85 cases of prostate cancer and 25 prostate cancer deaths among the 2,814 men and divided the group into thirds, based on the serum calcium level. "Comparing men in the top third with men in the bottom third, we found a significantly increased hazard for fatal prostate cancer.
"To our knowledge, this is the first study to examine prostate cancer risk in relation to serum calcium," Schwartz and Skinner wrote. "These results support the hypothesis that high serum calcium, or a factor strongly associated with it, such as high serum parathyroid hormone, increases the risk for fatal prostate cancer."
In an interview, Schwartz said that if the relationship between serum calcium and prostate cancer "turns out to be causal, it suggests a means for potentially reducing the risk of fatal disease through medicines that reduce serum levels of calcium and/or parathyroid hormone."
He added, "Both calcium and parathyroid hormone are known to promote the growth of prostate cancer cells in the laboratory."
Skinner said, "The take-home message is that this may offer a simple means to detect men who are at increased risk of fatal prostate cancer."