High Bone Density is Associated with Prostate Cancer in Older Afro-Caribbean Men: Tobago Prostate Survey

Objective: To test the hypothesis that bone mineral density (BMD), a possible surrogate of lifetime exposure to hormone/growth factor/vitamin D/calcium exposure, is higher in prostate cancer cases than controls.

Methods: Hip BMD was measured by dual X-ray absorptiometry in 222 Afro-Caribbean screening-detected prostate cancer cases and 1,503 screened non-cases, aged 45-79, in the population-based Tobago Prostate Survey. Because possible skeletal metastases may modulate BMD, men with prostate specific antigen >20 ng/ml or highly undifferentiated tumors (Gleason score > or = 8) were excluded. Mean BMD, adjusted for age and body mass index, was compared in cases and non-cases by analysis of variance. Risk across age group-specific BMD quartiles was compared using logistic regression.

Results: Overall, adjusted mean hip BMD was higher in cases (1.157 g/cm2) than non-cases (1.134 g/cm2) (p = 0.02). In men aged 60-79, prostate cancer risk was two-fold higher (OR, 2.12; 95% CI: 1.21-3.71) in the highest BMD quartile compared to the lowest. There was no association in younger men (interaction, p = 0.055).

Conclusions: High bone density is associated with prostate cancer among older men, consistent with an etiological role for lifetime exposure to factors which modulate bone density. However, other etiologies may dominate prostate cancer risk among younger men.