Fracture risk following bilateral orchiectomy.

PURPOSE: Bone loss has been reported in patients with prostate cancer treated with androgen deprivation therapy. We assess fracture risk following bilateral orchiectomy. MATERIALS AND METHODS: Through the Rochester Epidemiology Project we identified 429 Olmsted County, Minnesota men who underwent bilateral orchiectomy in 1956 to 2000, almost all for prostate cancer. Fractures were ascertained from comprehensive medical records and compared with expected numbers based on local incidence rates (standardized incidence ratio, SIR). Potential risk factors were assessed with proportional hazards models. RESULTS: During 1961 person-years of followup 161 men experienced 267 fractures, for a cumulative incidence after 15 years of 40% compared to 19% expected (p <0.001). However, 42 were pathological fractures and 82 were found incidentally on radiological surveys for metastasis. Overall fracture risk was increased (SIR 3.42, 95% CI 2.91-3.99) but was reduced by excluding the pathological and incidental fractures (SIR 2.04, 95% CI 1.66-2.47). The increase was largely accounted for by the moderate trauma fractures of the hip, spine and distal forearm traditionally linked with osteoporosis (SIR 3.50, 95% CI 2.71-4.43). In multivariate analyses risk factors for fractures generally included patient age, inactivity, prior radiological diagnosis of osteoporosis, chemotherapy and use of nonsteroidal antiandrogens, while independent risk factors for the traditional osteoporotic fractures included age, inactivity and diagnosis of osteoporosis. CONCLUSIONS: Fractures are common in men with prostate cancer due to advanced age, occurrence of pathological fractures and enhanced skeletal surveillance but there remains a significant increase in osteoporotic fracture risk following bilateral orchiectomy.