To examine Japanese patients who had received androgen-deprivation therapy (ADT) for longer periods, as it is known that ADT of patients with prostate cancer reduces their bone mineral density (BMD). However, our previous cross-sectional study revealed that short-term ADT (average, 23.5 months) does not significantly increase the prevalence of osteoporosis in Japanese patients.

The subjects consisted of 201 native Japanese patients with prostate cancer. They comprised 113 ADT-treated and 88 hormone-naive patients. Lumbar spine, total hip, and femoral neck BMDs were measured by dual-energy x-ray absorptiometry and expressed in standard deviation units relative to the scores of young adult men (T-score) or age-matched men (Z-score). Serum levels of bone metabolism markers were also measured.

The ADT-treated patients had significantly lower BMD values, T-scores, and even Z-scores than the hormone-naive patients (P <.001). For patients who were hormone-naive, ADT-treated for less than 2 years, and ADT-treated for more than 2 years, the osteoporosis prevalence was 4.5% (4/88), 12.1% (4/33), and 10.8% (4/37), respectively. The ADT-treated patients had significantly higher serum amino-terminal telopeptide levels than the hormone-naive patients (P = .014), but significantly lower serum carboxy-terminal telopeptide of type-I collagen levels than the ADT-treated patients with bone metastasis (P <.001).

Our cross-sectional study confirmed that both ADT-treated and hormone-naive Japanese patients with prostate cancer have low rates of osteoporosis. These findings are different from those of studies in western countries. Genetic and hormonal or other environmental factors may result in population differences in the characteristics of prostate cancer and BMD.