Biomarker for fatal prostate cancer found

NEW YORK (Reuters Health) - New research suggests that high levels of calcium in the bloodstream may increase a man's risk of dying from prostate cancer. If verified in future studies, determining levels of calcium in blood could assist doctors and patients in making decisions regarding treatment.

Ninety-nine percent of all of the calcium found in the body is in the bone. The remaining 1 percent of the calcium is ionized, or freely flowing in blood.

In a previous analysis of data from the National Health and Nutrition Examination Survey (NHANES I) study, Dr. Halcyon G. Skinner, at the University of Wisconsin-Madison, and Dr. Gary G. Schwartz at Wake Forest University in Winston-Salem, North Carolina, observed a link between elevated blood calcium levels and increased risk of fatal prostate cancer.

In their latest study, appearing this month in the journal Cancer Epidemiology, Biomarkers & Prevention, the researchers examined associations between blood calcium levels and prostate cancer fatalities among 6710 men evaluated between 1988 and 1994 for the NHANES III, which was linked to the National Death Index.

During an average of 5.3 years of follow-up, 25 men died of prostate cancer. The average age at death was 78.1 years.

Compared with men with the lowest levels, men with the highest levels of total blood calcium had about a twofold higher risk of dying from prostate cancer, after adjusting for social and demographic factors, body weight, and general health status.

The risk of death was threefold higher in men with the highest versus the lowest levels of ionized calcium. After excluding three men who died within the first 3 years of follow-up, the relative risk of death was 4.65-fold higher in men with the highest ionized calcium levels.

In a Wake Forest press release, Schwartz noted that most prostate cancers are slow-growing and many men will die with, rather than of, their prostate cancer and many men with prostate cancer are treated unnecessarily.

"These new findings, if confirmed, suggest that men in the lower end of the normal distribution of ionized serum calcium are three times less likely than men in the upper distribution to develop fatal disease," Schwartz said.

"These men may choose to delay treatment or perhaps defer it altogether," he added. "It also suggests that medicine may be able to help in lowering the risk of fatal prostate cancer by reducing serum calcium levels."

Schwartz cautioned that the level of calcium in blood is not influenced all that much by calcium in the diet. Blood calcium levels are controlled genetically and are stable over much of a person's life. "These results do not imply that men need to quit drinking milk or avoid calcium in their diets," Schwartz said.

SOURCE: Cancer Epidemiology, Biomarkers and Prevention, February 2009.