Changes in bone mineral density in men starting androgen deprivation therapy and the protective role of vitamin D.

Summary: Androgen deprivation therapy in 80 men was associated with declines in bone mineral density (BMD), which were greatest in the first year, and in the lumbar spine compared to controls. Vitamin D use was associated with improved BMD in the lumbar spine and in the first year.

Introduction: Decreased BMD is a common side effect of androgen deprivation therapy (ADT), leading to increased risk of fractures. Although loss of BMD appears to be greatest within the first year of starting ADT, there are few long-term studies of change in BMD, and risk factors for bone loss are not well-characterized.

Methods: Men aged 50+ with nonmetastatic prostate cancer starting continuous ADT were enrolled in a prospective longitudinal study. BMD was determined by dual-energy x-ray absorptiometry at baseline and yearly for 3 years. Matched controls were men with prostate cancer not receiving ADT. Multivariable regression analysis examined predictors of BMD loss.

Results: Eighty ADT users and 80 controls were enrolled (mean age 69 years); 52.5 % had osteopenia and 8.1 % had osteoporosis at baseline. After 1 year, in adjusted models, ADT was associated with significant losses in lumbar spine BMD compared to controls (-2.57 %, p = 0.006), with a trend towards greater declines at the total hip (p = 0.09). BMD changes in years 2 and 3 were much smaller and not statistically different from controls. Use of vitamin D but not calcium was associated with improved BMD in the lumbar spine in year 1 (+6.19 %, p < 0.001) with smaller nonsignificant increases at other sites (+0.86 % femoral neck, +0.86 % total hip, p > 0.10) primarily in the first year.

Conclusions: Loss of BMD associated with ADT is greatest at the lumbar spine and in the first year. Vitamin D but not calcium may be protective particularly in the first year of ADT use.