Adjuvant Effect of IV Clodronate on the Delay of Bone Metastasis in High-Risk Prostate Cancer Patients: A Prospective Study

PURPOSE: High-risk prostate cancer patients undergoing treatment often experience biochemical recurrence. The use of bisphosphonates as an adjuvant treatment delays skeletal events, yet whether or not bisphosphonates also delay metastastic development remains to be determined. MATERIALS AND METHODS: A total of 140 high-risk prostate cancer patients who were undergoing definitive treatment and who had clinically organ-confined disease and who suffered from biochemical recurrence were administered intravenous (IV) clodronate. The patients were treated with a radical retropubic prostatectomy (RP) or curative radiotherapy (RTx). Upon androgen deprivation therapy initiation, tri-monthly IV clodronate was added to the treatment to prevent bone demineralization. Twenty-six out of 60 operated cases and 45 out of 80 irradiated cases received bisphosphonate. The length of time until the first bone metastasis was recorded and analyzed. RESULTS: No statistical difference was found for the type of primary treatment (RP or RTx) on the time to the first bone metastasis (95% confidence interval [CI], 0.40 to 2.43; p=0.98). However, there was a clear advantage favoring the group that received bisphosphonate (p<0.001). The addition of bisphosphonate delayed the appearance of the first bone metastasis by seven-fold (95% CI, 3.1 to 15.4; p<0.001). CONCLUSION: Treatment with tri-monthly IV clodronate delayed the time to the first bone metastasis in high-risk prostate cancer patients who were experiencing an increase in the prostate specific antigen level after definitive treatment.