The effects of intermittent androgen deprivation therapy (ADT) and zoledronic acid administration on bone density in patients with prostate cancer

Abstract

15593 Background: Intermittent ADT is commonly used in men with recurrent prostate cancer. Bone loss associated with ADT is well described. Bisphosphonate use in men undergoing ADT results in improvement in bone mineral density (BMD), although the utility and duration of bisphosphonate use in men undergoing intermittent ADT are unclear. Objective:To evaluate the effect of zoledronic acid administration every 3 months on BMD in men with prostate cancer undergoing intermittent ADT, and whether BMD is maintained upon discontinuation of both ADT and zoledronic acid. Methods: Patients with recurrent prostate cancer starting ADT were eligible to participate. Subjects received ADT for 9 months in addition to 3 doses of zoledronic acid every 3 months. At 9 months, patients who achieved an undetectable serum PSA were taken off ADT and then randomized either to continuing zoledronic acid every 3 months for an additional 3 doses vs. observation. BMD, assessed by DEXA scan, was determined at baseline, 9 months, and between 18 -24 months at hip, trochanter, femoral neck and lumbar spine sites. Results: Twenty two patients were treated with ADT and zoledronic acid between 2003–2006. Seven of these subjects had bone metastases and had previous treatment with ADT.There was one infusion related reaction, and one patient developed osteonecrosis of the jaw and was removed from the study. At baseline, 3 patients had osteoporosis at the lumbar spine. All patients who received zoledronic acid for 9 months had an improvement in BMD at all 3 sites. In the 7 subjects who had previously received ADT, BMD of the femoral neck increased significantly by approximately 1.9%. Among the 6 patients randomized to continuing zoledronic acid after discontinuing ADT at 9 months, all had a further, significant increase in BMD. Those randomized to observation were unable to maintain their BMD and had continued bone loss despite stopping ADT. Conclusions: This small study demonstrated an increase/maintenance of BMD in men receiving intermittent ADT and zoledronic acid. Only those men who continued zoledronic acid for up to a total of 9 mos after discontinuing ADT maintained BMD No significant financial relationships to disclose.