Men with elevated levels of calcium in their blood may have a much higher risk of getting fatal prostate cancer, US researchers said on Wednesday.

The findings indicate that a simple blood test may identify men at high risk for the most dangerous prostate tumors, and there already are drugs available that cut calcium levels in the bloodstream, the researchers said.

They tracked 2,814 men in a US government health survey in which they gave blood samples that revealed calcium levels. The men in the top third of blood calcium levels had 2.68 times the risk of developing fatal prostate cancer later in life compared to those in the bottom third, the study found.

"If serum calcium really does increase your risk for fatal prostate cancer, that's wonderfully exciting because serum calcium levels can be changed," Gary Schwartz of Wake Forest University School of Medicine, who helped lead the study, said in a telephone interview.

"One way to think of it is to think of the tremendous advances in the control of cardiovascular disease that occur from understanding that things like serum cholesterol predict heart attack," Schwartz added.

Doctors have struggled to find ways to predict if a man who gets prostate cancer will have a tumor that poses little danger, as is often the case, or one that is a killer.

Blood calcium was not very predictive of whether a man would get nonlethal prostate cancer, but was highly predictive of whether a man would get a fatal case, the researchers wrote in the American Association for Cancer Research's journal Cancer Epidemiology, Biomarkers & Prevention. The blood samples on average were given a decade before the cancer appeared, the researchers said.

A COMMON CANCER

Prostate cancer is the second most commonly diagnosed form of cancer in men worldwide, with about 780,000 men diagnosed per year, and the sixth mostly deadly form in men, with about 250,000 deaths per year, the American Cancer Society said. 

High Blood Calcium tied to Cancer

Schwartz said it is unclear whether it is the actual calcium or blood levels of parathyroid hormone, which is supposed to keep calcium levels at normal levels in the bloodstream, that is raising the risk. Either way, he said there are drugs that can lower them, including Fontus Pharmaceuticals Inc's Rocaltrol, also called calcitriol; Genzyme Corp's Hectorol (doxercalciferol); Abbott Laboratories' Zemplar (paricalcitol); and Amgen Inc's Sensipar (cinacalcet).

People treated for high blood calcium usually have chronicKidney disease, which is associated with low vitamin D levels. Low vitamin D levels elevate parathyroid hormone levels, Schwartz said.

Halcyon Skinner of the University of Wisconsin, who also worked on the study, said there is little relationship between calcium in the diet and blood calcium levels, so these men would not benefit from eating less food rich in calcium.

Previous research had suggested a role for calcium in prostate cancer. In laboratory studies, parathyroid hormone and calcium promote the growth of prostate cancer cells.