Vertebral fractures and the misclassification of osteoporosis in men with prostate cancer

Abstract

Androgen deprivation therapy (ADT) has become the cornerstone of treatment for both advanced and nonmetastatic prostate cancer. The presence of a nontraumatic vertebral fracture (VF) identifies a patient who has clinical osteoporosis. Vertebral fracture analysis (VFA), a dual-energy X-ray absorptiometry (DXA)-based technology identifies VFs in conjunction with a standard bone mineral density (BMD) examination. The objective of this study was to determine if VFA would increase the diagnosis of osteoporosis in men with prostate cancer on ADT. One hundred sixteen men aged ≥ 60yrs with nonmetastatic prostate cancer receiving ADT for ≥ 6mos underwent DXA of the spine, hip, and 1/3 distal radius, VFA, and conventional vertebral X-rays. Approximately 40% of the men had clinically defined osteoporosis. The use of conventional DXA criteria (spine and hip) alone resulted in the misdiagnosis of approx 75% of patients. VFA and addition of the 1/3 distal radius site performed by DXA both increased the rate of diagnosis and reduced the misclassification of osteoporosis in men with prostate cancer, compared with conventional DXA criteria alone. Analysis indicated that VFA assessment of mild, moderate, and severe fractures from all readable vertebrae (T5-L4) had a kappa statistic, sensitivity, and specificity of 0.92, 100%, and 95%, respectively, with semiquantitative radiography. Men with prostate cancer on ADT should be screened for osteoporosis at the initiation of therapy, and evaluation should include DXA of the 1/3 distal radius in addition to the spine and hip, as well as evaluation for VFs.