The incidence of prostate cancer (PCa) in Australia and New Zealand is one of the highest worldwide1 . Prostate cancer has the propensity to metastasize to bone, which leads to skeletal related events namely bone pain2 . The skeletal metastases observed in this disease are characteristically blastic with increased local bone density demonstrable on imaging3 . Once patients with advanced PCa are prescribed androgen deprivation therapy (ADT) significant bone loss is observed (2-4% within 12 months of initiation) which leads to osteoporosis4 . While most research in PCa and bone health focuses on declining bone mass, few studies have investigated the effects of PCa prior to ADT initiation on bone mineral density (BMD).
In order to explore the possible effects of PCa on BMD prior to ADT commencement, data from the Dubbo Osteoporosis Epidemiology Study (DOES) was analysed. Lumbar spine BMD and femoral neck BMD in participants with incident PCa (n=36) were compared to the remaining male DOES cohort (n=701).
Lumbar spine BMD was highest among PCa participants not on ADT (1.40g/cm2) followed by controls (1.29g/cm2) and PCa participants on ADT (1.21g/cm2). A similar trend was observed at the femoral neck. Although the differences in BMD are not statistically different (P>0.05), they are clinically significant as they are close to the standard deviation (0.135g/cm2) used to derive the T-score, which is used to diagnose osteoporosis. Interestingly, the magnitude of the difference in BMD is not observed when comparing baseline BMD of participants who will later develop PCa with controls (1.26g/cm2 v/s 1.26g/cm2 at lumbar spine, P>0.05).
The data presented here reinforce the osteosclerotic effects of PCa while indicating that such effects may occur prior to metastasis. This may warrant monitoring of BMD prior to ADT initiation in this group of patients.