Dynamics of bone mineral density during intermittent androgen deprivation for men with biochemical recurrence of prostate cancer.

Abstract

4558 Background: Androgen deprivation therapy (ADT) for prostate cancer leads to loss of bone mineral density (BMD) and increased fracture risk. We hypothesize that intermittent ADT (IADT) may attenuate BMD loss. Methods: Patients with rising PSA after surgery (RP) or radiation (RT) received IADT in a prospective clinical trial. After 9 months “on treatment” with leuprolide and flutamide, ADT was stopped and monthly PSA levels were measured during the “off treatment” interval until a threshold PSA (1 ng/mL for RP, 4 ng/mL for RT) was met. At that time, ADT was resumed in another cycle and patients were treated intermittently in this manner until castration resistance. Standardized average dual energy X-ray absorptiometry (DXA) scans of lumbar spine and left hip were performed at baseline and at each change in therapy. Men who completed at least one entire treatment cycle and who underwent at least 3 DXA scans were eligible for analysis. Results: Forty-eight of 100 patients met criteria. Mean spine BMD decreased 3.1% (p<0.0001) while mean hip BMD decreased 1.0% (p=0.005) during first “on treatment” interval. Significant gains were made in mean spine BMD of 1.8% (p=0.001) but not in the hip during first “off treatment” interval. Subsequent cycles of IADT also revealed attenuation of “on treatment” losses during “off treatment” intervals, though few achieved statistical significance (see table). Despite regained BMD during “off treatment” intervals, the net result for the first cycle was loss of 1.3% (p=0.08) at the spine and 1.0% (p=0.02) at the hip. Conclusions: ADT-induced loss of BMD is attenuated during the “off treatment” intervals of IADT. However, BMD does not return to baseline, sustaining only a smaller net loss. Cycle Lumbar spine Left hip N Mean BMDg/cm2 (% change) N Mean BMD g/cm2 (% change) 1 On 48 (−3.1) 48 (−1.0) Off 47 (1.8) 48 (−0.1) 2 On 38 (−0.7) 37 (0.4) Off 28 (1.2) 28 (0.2) 3 On 31 (0.1) 29 (−0.6) Off 24 (2.3) 23 (−0.1) 4 On 23 (−1.1) 20 (−0.4) Off 16 (0.4) 15 (−0.5) No significant financial relationships to disclose.