Fracture risk in patients with prostate cancer on androgen deprivation therapy

Although a decrease in bone mass is a well-known side effect of hormone therapy for prostate carcinoma, its clinical significance is unclear, as there is only scanty information about the incidence of fractures. Therefore, the aim of this study was to determine the risk of non-metastatic fractures in patients with prostate cancer undergoing androgen deprivation therapy. We performed a retrospective cohort study that comprised 288 patients with cancer who were subjected to androgen deprivation therapy (ADT). All were given LHRH agonists, and most of them also received peripheral androgen receptor blockers. The results were compared with a control group of 300 men that were not receiving ADT. The incidence rates of peripheral and vertebral fractures in the group of men on ADT were 1.9 and 0.8 per 100 patient-years, respectively. Incidence rates in the control group were 0.5 and 0.2, respectively. In the whole study group, 35 patients had at least one fracture during follow-up (25 on ADT, ten controls). Thus, the number of patients with at least one fracture was significantly higher in the group on ADT (P=0.001 by the log-rank test). The unadjusted risk ratio was 4.2 (CI 2.0-8.9). A similar value (risk ratio 3.6; CI 1.6-7.7, P=0.001) was found after it was adjusted for other factors, such as age or prior fractures. Therefore, ADT is associated with a fourfold increase in the incidence rate of both peripheral and vertebral fractures. Although the absolute incidence remains relatively small, preventive measures should be considered for high-risk patients.