Cross-sectional study of bone turnover during bicalutamide monotherapy for prostate cancer.

Objectives: Monotherapy with bicalutamide increases serum concentrations of testosterone and estradiol. Because estrogens play an important role in male bone metabolism, bicalutamide monotherapy may have fewer adverse effects on bone than androgen-deprivation therapy with a gonadotropin-releasing hormone agonist.

Methods: In a cross-sectional study, we compared gonadal steroid levels and biochemical markers of bone turnover among three groups of men with prostate cancer: hormone-naive men, men treated with a gonadotropin-releasing hormone agonist, and men receiving bicalutamide monotherapy. Men with bone metastases or metabolic bone disease were excluded. Fifty-five eligible subjects were included in the analyses.

Results: Serum testosterone and estradiol concentrations were lower in men treated with a gonadotropin-releasing hormone agonist than in hormone-naive men or men receiving bicalutamide monotherapy (P <0.001 for each comparison). Serum testosterone and estradiol concentrations were higher in men receiving bicalutamide monotherapy than in the hormone-naive men (P <0.001). The mean serum urinary excretion of deoxypyridinoline, urinary excretion of N-telopeptide, and serum osteocalcin were significantly higher in men treated with a gonadotropin-releasing hormone agonist than in the other groups (P <0.05 for each comparison). In contrast, biochemical markers of bone turnover were similar for hormone-naive men and men receiving bicalutamide monotherapy (P >0.05 for each comparison).

Conclusions: Biochemical markers of bone turnover are elevated in men receiving gonadotropin-releasing hormone agonist treatment but not in men receiving bicalutamide monotherapy. These observations suggest that bicalutamide monotherapy may maintain bone mineral density and prevent fractures.