Considering that bone loss is a known side effect of androgen-deprivation therapy (ADT) for men with prostate cancer (PCa), it might seem logical that calcium and vitamin D supplementation would help manage this consequence.
Not necessarily, explains PCa epidemiologist Gary G. Schwartz, PhD, MPH, of Wake Forest Baptist Medical Center in Winston-Salem, N.C. He and co-investigator Mridul Datta uncovered data that demonstrate such supplementation can increase the risk of cardiovascular disease and, ironically, aggressive PCa (The Oncologist 2012;17:1171–1179;).
What made you start suspecting that calcium and vitamin D supplementation might actually do more harm than good in men suffering ADT-related bone loss?
Dr. Schwartz: Many urologists have presumed that, with respect to PCa, dietary calcium is beneficial, or is at least benign. Conversely, many epidemiologic studies have implicated dietary calcium with an increased risk of PCa. Recent prospective studies also report an increased risk of fatal PCa for men with higher levels of calcium in blood (Cancer Epidemiol Biomarkers Prev 2012;21:1768-1773). Although the mechanisms underlying the association between calcium and PCa are incompletely understood, many cancer epidemiologists regard dietary calcium as a probable prostate carcinogen.
Do you think urologists should stop prescribing such supplementation until more studies are done?
Dr. Schwartz: That’s a tough question. My guess is that, like many treatment decisions in PCa, the decision whether or not to take calcium supplements may need to be individualized based on clinical judgment and patients’ wishes.
So calcium supplements, rather than vitamin D supplementation or a combination of the two, are the main problem?
Dr. Schwartz: I do think that calcium is the culprit, since vitamin D seems to have a beneficial effect on prostate cells. However, in practice, vitamin D and calcium are often taken together.
The vitamin D is probably protective—there is a wealth of papers on that one (Ann Epidemiol 2009;19:96-102).
If you don’t believe that stopping supplementation is the right strategy at this time, how do you think urologists should proceed at this point in terms of prescribing such supplementation for these patients?
Dr. Schwartz: Common sense suggests caution regarding calcium supplements in patients with a history of significant cardiovascular disease.
What sort of reaction has your finding evoked in the urology community? As you pointed out in your report, many professional and lay groups advocate calcium and/or vitamin D supplementation for men undergoing ADT.
Dr. Schwartz: The first reaction of many urologists and oncologists was surprise. However, in my experience, the urologic community is a very pragmatic one. Thus, after the initial reaction, the response quickly became, “What do we do now?”