Mortality following hip fractures in men with prostate cancer.

Abstract

49 Background: Rapid loss of bone-mineral density is a known side-effect of androgen deprivation therapy (ADT) for prostate cancer (PCa). Hip fractures are also independently associated with risk of mortality. To our knowledge few population-based observational studies have yet investigated the risk of dying following fractures among men with PCa. We aimed to assess skeletal-related events and mortality in more detail by specifically studying the link between hip fractures in PCa men and risk of death. Methods: PCBaSe Sweden 2.0 is based on the National Prostate Cancer Register and contains age and county matched men free of PCa. We selected all men (n=14,205) who had been hospitalized with a hip fracture, as registered in the National Patient Register, between 2006 and 2010. A total of 2300 were diagnosed with PCa before the hip fracture and 66% of them were treated with ADT. The main outcome was death as registered in the National Cause of Death Register. The risk of death was estimated using multivariate Cox Proportional Hazards regression analyses and standardized mortality ratios (SMRs) taking into account PCa risk category, history of fractures, civil status, Charlson Comorbidity Index, and treatment with bisphosphonates. Results: In the analysis for risk of death >90 days after a hip fracture, there was an increased risk of death among PCa men on ADT, especially those aged <84 years (e.g., HR at 3-6 months after hip fracture: 2.47 (95%CI: 1.85-3.30) compared to men free of PCa with a hip fracture). The SMRs showed that PCa men on ADT who got a hip fracture were seven times more likely to die than expected in the reference population of all men with PCa, whereas PCa men who were not on ADT and had a hip fracture were 13 times more likely to die than expected in this reference population. However, the absolute risk difference between men with and without a hip fracture was 30 per 1,000 person-years when evaluating the effect of a hip fracturing among men on ADT, whereas a hip fracture would cause an additional 20 per 1,000 person-years to die among PCa men without ADT as well as among men free of PCa. Conclusions: Our SMRs and absolute risk calculations show that hip fractures are more dangerous in PCa men treated with ADT than in PCa men without ADT or in men free of PCa.