Titration of dosage of the protective effect of zoledronic acid in patients submitted to androgen-deprivation therapy due to CaP

15561 Background: Androgen-deprivation therapy is gold-standard treatment for advanced CaP. Zoledronic acid has become a new adjuvant drug for osteoporosis prevention and pain control in patients submitted to androgen-deprivation therapy but regimen of administration is not consensual. Many off-label regimens are used on different occasions. Methods: 64 patients (mean age: 71.7 y-o) after being diagnosed with non-intended to cure therapy were initiated with androgen-deprivation with LHRH agonists at the same time they initiated no treatment (control-16 cases) or monthly (12), bi- monhtly (10), tri-monthly (14) or semestral (12) zoledronic acid infusions for 24 months. Lumbar BMD were evaluated periodically with dual- energy X-ray absorptiometry with densitometry in L2-L4 at 6-month intervals. Tuckey-Kramer and Scheffe`s tests were used for statistical significance of 0.05. Results: Control patients revealed a subgroup showing progressive diminishing BMD along the studied period while another sub-group remained stable. Patients receiving treatment with zoledronic acid showed increasing BMD at the lumbar area (p <0.05) for the 4 treated groups. The protective effects of lumbar BMD were remarkable starting at 18 months in the 4 treated groups with progressive increase of BMD with no clear advantage to any particular regimen (p >0.05). Bone protection could be achieved in the 4 treated groups with no differences for the monthly, bimestral, trimestral or semestral infusions. Conclusions: Zoledronic acid is effective in decreasing bone loss after androgen-deprivation therapy compared to no treatment for osteoporosis. Titration of the dosage regimen of the infusions showed no statistical advantage for any temporal regimen. Reasons for that can only be speculative at this time. [Table: see text] No significant financial relationships to disclose.