Zoledronic acid therapy impacts risk and frequency of skeletal complications and follow-up duration in prostate cancer patients with bone metastasis

To evaluate the effects of timing and length of zoledronic acid (ZA) treatment on outcomes for patients with prostate cancer in clinical practice. Patients with prostate cancer and first bone metastasis diagnosed from January 2003 to October 2006 were included. Patients were considered 'untreated' if no ZA was given, 'early ZA-treated' if ZA was initiated before skeletal complication (SC) occurrence or 'late ZA-treated' if one or more SC was documented before or at ZA initiation. Patients were classified with short (90 days), medium (91-180 days) or long (> 180 days) treatment persistence. Assessments included follow-up duration (FUP) and risk of developing one or more SC. Among eligible patients, 847 were untreated, 243 were early ZA-treated and 218 were late ZA-treated. For untreated versus early ZA-treated groups, median FUP was 263 versus 357 days (p < 0.0001), respectively, and time to first SC was 199 versus 273 days (p < 0.0001), respectively. ZA treatment was associated with significantly longer FUP and lower SC risk. The early ZA-treated group had significantly longer FUP versus the late ZA-treated group (median days, 357 vs. 299.5); the late ZA-treated group experienced significantly higher SC risk vs. the early ZA-treated group (odds ratio, 1.51). Compared with the long-persistence group, FUP was 56% and 40% shorter in the short and medium groups, respectively (p < 0.0001). Treatment with and early initiation of ZA for patients with prostate cancer and bone metastasis significantly prolonged time to and reduced risk of developing SC, while extending FUP.