White race and low bone mineral density (osteoporosis) appear to be the only two of a dozen different potential risk factors that significantly increase the likelihood of vertebral (spinal and hip) fractures among men being treated with androgen deprivation therapy (ADT) for prostate cancer.
It is well known that treatment with ADT can lead to a reduction in bone mineral density and an increase in risk for bone fractures in men with prostate cancer. Saylor et al., in a paper currently in press in the Journal of Urology, have carried out a re-analysis of data from a Phase III clinical trial of a potential agent for the prevention of fractures in men being treated with ADT. (This would appear to have been the recent trial of toremifene vs. a placebo, which did not show a statistically significant outcome in favor of toremifene.)
The goal of this re-analysis was to evaluate whether a series of specific risk factors made it more likely that trial participants would have vertebral fractures at the time of trial entry or over the course of the trial. Trial participants were all men receiving ADT for prostate cancer. They were all either 70 years of age or older or they were known to have low bone mineral density if they were younger than 70 years of age.
The results of the re-analysis were as follows:
- The trial enrolled a total of 1,244 patients.
- 896 patients were of white race.
- 348 patients were of non-white race.
- 162/1,244 patients (13.0 percent) already had a vertebral fracture at baseline (i.e., at time of enrollment).
- Only two factors appeared to be significantly associated with and increased risk for vertebral fractures among the study population.
- White race (compared with non-white race, p = 0.028)
- Osteoporosis (at any site, p = 0.002; at the spine, p = 0.053; and at the hip, p = 0.002).
- Factors not associated with vertebral fractures included
- The patient’s age
- Country of residence (USA vs. Mexico)
- Duration of ADT at baseline
- Type of ADT (LHRH agonist vs. orchietomy)
- Body mass index
- Levels of a variety of biochemical markers (testosterone, estradiol, C-telopeptide, bone-specific alkaline phosphatase and osteocalcin).
- Similar results were obtained when analysis was restricted exclusively to the patients ≥ 70 years of age.