Management of osteoporosis in men on androgen deprivation therapy

Osteoporosis is a common consequence of androgen deprivation therapy (ADT) for prostate cancer. Up to 20% of men on ADT for localized prostate cancer will fracture within 5 years. Fortunately, generally safe and effect therapy is available. Although once considered non-controversial, there is some concern about calcium supplementation, but all studies of osteoporosis therapy in men have included calcium. In most older men, serum 25-hydroxyvitamin D levels are likely to be low, although again there is controversy about the ideal level. Many experts believe that all older men, including those on ADT, need to have a level of >30 ng/ml, which is easily accomplished. Bone mineral density (BMD) testing by dual energy X-ray absorptiometry (DXA) is indicated for men on ADT. Interestingly, forearm DXA may be particularly important in ADT men, in addition to spine and hip. Some experts have suggested that men on ADT with a T-score of ≤-1.5 should be treated. Alternatively FRAX or another risk calculator can be used. Oral and intravenous bisphosphonates are FDA approved treatments for men with osteoporosis and increase BMD in men on ADT. Potential off-label agents include raloxifene and toremifene. The latter and denosumab have been shown to increase bone density and decrease vertebral fractures in men on ADT. Raloxifene and denosumab are only FDA approved for postmenopausal osteoporosis. Thus, prevention of fractures can be accomplished in this high risk population.