Peripheral or Axial Bone Density Measurements to Identify Osteoporosis in Prostate Cancer Patients Undergoing Androgen Deprivation Therapy?

ObjectivesTo compare aDEXA and pDEXA in patients with advanced prostate cancer (PCa) undergoing androgen deprivation therapy (ADT). A significant proportion of patients presenting with advanced PCa are osteoporotic, and many will become so because of ADT. Guidelines have recommended bone densitometry assessment before beginning ADT, with subsequent monitoring. However, axial dual energy x-ray absorptiometry (aDEXA) scanners, being large, expensive, and hospital-based, are not always widely available. Peripheral DEXA (pDEXA), with portable, office-based machines can be used, but the results have mostly been compared with aDEXA in women without cancer.MethodsA total of 73 men (mean age 76 years) with advanced PCa, who were receiving ADT and found to be osteoporotic (T score ≤−2.5) on pDEXA (Osteometer-DTX200) were also scanned by aDEXA (Hologic-QDR 4500 DEXA). Comparisons were made between the bone mineral density measurements of the ultradistal forearm and axial sites.ResultsThe mean ± SD T score of the forearm, femoral neck, total hip, and lumbar spine was −3.4 ± 0.8, −2.6 ± 1.0, −1.8 ± 0.9, and −0.8 ± 1.3, respectively. Of the 73 men, 67, 61, and 39 were found to be osteoporotic or osteopenic at the femoral neck, total hip, and lumbar spine, respectively. The correlation coefficients between the forearm and axial T scores were all significant (P < .05): femoral neck, r = 0.32, total hip, r = 0.34, lumbar spine, r = 0.24.ConclusionsWhen osteoporosis is diagnosed on pDEXA, most patients with PCa will be either osteoporotic or osteopenic at the hip, but a large proportion will be normal at the lumbar spine. In this setting, lumbar DEXA might be less reliable at predicting the fracture risk probably owing to calcification and degenerative changes.