low calcium predicts bone loss in prostate cancer

By Amy Norton
NEW YORK (Reuters Health) - Men who are about to undergo hormone-suppressing therapy for prostate cancer may want to bump up their levels of calcium, a new study suggests.
Researchers found that more than half of the 372 men in their study who underwent androgen-deprivation therapy developed the bone-thinning disease osteoporosis. Those with a low calcium intake appeared to be at particular risk, the study authors report in the journal BJU International.
Suppressing testosterone and other androgen hormones helps control the growth and spread of prostate tumors. But it also causes a drop in bone density, which means that osteoporosis is a common side effect of the therapy.
However, the new findings highlight how important adequate calcium levels are for preventing this risk, according to the researchers. The results suggest that men on androgen deprivation therapy should be sure to get at least 1,000 milligrams (mg) of calcium each day, lead study author Dr. Jacques Planas told Reuters Health.
Other bone-protecting measures, like getting adequate vitamin D and not smoking, are also recommended, according to Planas and his colleagues at Autonoma University School of Medicine in Barcelona.
The findings are based on bone density measurements from men with prostate cancer that had not spread to the bone. Of the 266 men undergoing hormonal therapy, 55 percent had osteoporosis. In addition, a surprisingly high 35 percent of 106 men treated with surgery also had the bone disease.
Overall, the average calcium intake was lower among men with osteoporosis, at 610 mg per day, versus 683 mg for men without the disease. When Planas and his colleagues considered other factors, like the men's age, calcium intake turned out to be an independent predictor of osteoporosis risk.
It's not clear why men undergoing surgery had such a high rate of osteoporosis, said Planas. "We are studying if prostate cancer itself may be responsible, secreting different molecules which may have an influence on bone mineral density," he said.
But while calcium and vitamin D supplements might be important for men undergoing androgen-deprivation therapy, they should not necessarily bump up their intake of dairy products, which are a source of saturated fat, according to an editorial published with the report.
One large study of prostate cancer patients found that those with the highest fat intake were three times more likely to die over 5 years than those with the lowest fat consumption, notes Dr. Nigel J. Parr of the Wirral Trust Hospital in the UK.
His own research, Parr has found evidence that a very low-fat diet might help slow the progression of prostate cancer.
"Thus," he writes, "caution should be adopted before advocating an increase in dairy (foods) in patients with prostate cancer."
SOURCE: BJU International, April 2007.