The relationship between serum testosterone and bone mineral density in Japanese men and the effects zoledronic acid in prostate cancer patients with low serum testosterone

Abstract

Although hormone therapy is definitely beneficial for patients with prostate cancer, a decrease in bone mineral density and an increased risk of fracture have been noted as adverse events. Improving bone metabolism in these patients is especially important in an aging society. We herein report the results of two studies: the first examined the effect of low serum testosterone levels on bone mineral density in a large number of Japanese men; the second study investigated the effect of a 12-month formulation of zoledronic acid injection for multiple years in prostate cancer patients with castration levels of serum testosterone due to androgen deprivation therapy. The first study included 1112 patients with late-onset hypogonadism. A multiple regression analysis that included factors that were significant in the simple regression analysis showed that only age (p < 0.001) and testosterone (p = 0.013) were significantly associated with bone mineral density. A significant relationship between serum testosterone and bone mineral density was also found in an age-adjusted regression analysis (p = 0.008) and a trend analysis (Ptrend = 0.001). The second study included 12 prostate cancer patients with castration levels of serum testosterone due to androgen deprivation therapy, and who had received a 12month formulation of zoledronic acid injection for multiple years. A trend analysis clearly showed that bone mineral density tended to increase year by year during the 4-year observation period (Ptrend < 0.001). In addition, we found no treatment-related adverse events in patients who received long-acting zoledronic acid. Thus, we conclude that men with lower serum testosterone levels are likely to have reduced bone mineral density and wish to emphasize that bone mineral density can be increased in prostate cancer patients by the continuous administration of long-acting zoledronic acid at 12month intervals, even when their serum testosterone levels are below castration level.