Bone mineral density increases were seen in prostate cancer patients on ADT who took the drug for two years.

STOCKHOLM—Treatment with zoledronic acid for two years in men who are undergoing androgen deprivation therapy (ADT) for prostate cancer is usually well tolerated and effective for preventing bone loss, new findings suggest.

“Our results confirm and extend results from earlier one-year studies showing that the bisphosphonate zoledronic acid can increase BMD [bone mineral density] beyond baseline levels in prostate cancer patients who are receiving ADT,” the researchers reported in a poster presentation at the 33rd Congress of the European Society of Medical Oncology.

Richard Casey, MD, director of CMX Research in Oakville, Ont., Canada, and his colleagues evaluated the two-year efficacy and safety of zoledronic acid initiated for the treatment of bone loss either up front or after one year of ADT with goserelin. ADT reduces BMD by 2.4%-9.6% each year and progressively increases fracture risk in men with prostate cancer, the authors noted.

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The trial, which involved 153 hormone-naïve men with locally advanced prostate cancer who had no bone metastases and were starting ADT with goserelin, consisted of two phases. In the first phase, the men were randomized to a treatment or control arm. The treatment arm received zoledronic acid in addition to goserelin and the control arm receive goserelin alone; each agent was administered every three months for 12 months.

In the second phase, patients assigned to zoledronic acid continued treatment for an additional 12 months (zoledronic acid/zoledronic acid). Patients initially assigned to goserelin alone who chose to remain on goserelin were randomized to treatment with goserelin alone (goserelin/goserelin) or goserelin plus zoledronic acid (goserelin/zoledronic acid) for another 12 months. The primary end point of the second phase of the trial was percent change in lumbar spine BMD from baseline to month 24.

At 24 months, lumbar-spine BMD scores had increased by 2.75 g/cm2 in the zoledronic acid/zoledronic acid group but decreased by 0.89 g/cm2 in the goserelin/zoledronic acid group and 2.51 g/cm2 in the goserelin/goserelin group.

Overall, the data show that up-front treatment with zoledronic acid seems to be more effective at preventing BMD loss than starting zoledronic acid after the first year of ADT, he said.

During the second phase of the trial, the combination of goserelin/zoledronic acid was generally well tolerated, with no serious adverse events observed.