Solid tumor cancer patients treated with zoledronic acid experienced reduced skeletal related events as compared to untreated patients in clinical practice claims database

Abstract

6596 Background: Patients (pts) with bone metastasis are at high risk for skeletal related events (SREs), leading to increased morbidity, mortality, and decreased QOL. Methods: To study the impact of zoledronic acid on SRE rates, follow-up duration (from 1st bone metastasis diagnosis to last claim) in treated pts as compared to the experience of non bisphosphonate-treated pts (untreated), and to investigate relative impact of zoledronic acid (ZA) frequency of administration using data from PharMetrics integrated claims database of 80 health plans across the U.S, from Jan 02 to Oct. 05. Results: There were 1,518 ZA treated-pts and 3308 untreated-pts, who met study inclusion criteria of having breast, prostate, or lung cancers, with confirmed bone metastasis and SRE experience. At baseline, breast cancer pts (N=1,799) had lowest Charlson Co-morbidity Index (CCI); lung cancer pts (N=2,413) had highest CCI (p<0.05). Prostate cancer pts (N=622) were significantly older (p<0.05). The average monthly ZA prescription rate (Rx) was 0.73 with average total Rxs of 7.82 over the follow-up duration. ZA use reduced monthly SRE rate by 30% from 0.41 ± 0.4 in untreated pts to 0.29 ± 0.3 in treated pts (p<0.001) and prolonged follow-up durations in months from 9.4 ± 9.8 in untreated to 12.2 ± 9.0 in treated pts (p<0.001). Regression models of SRE rate or follow-up duration as the dependent variable investigating the impact of ZA prescribing patterns indicated that pts who followed ZA label dose of 4 mg every q3, q4 experienced the lowest SRE rate (p<0.001) and had longer follow-up duration (p<0.005) as compared untreated pts. ZA use almost doubled time to 1st SRE from 101±165 days in untreated pts, to 185±210 days in treated pts (p<0.0001). ZA also delayed time between 1st to 2nd SRE from 85 days in untreated to 111 days in treated pts (p<0.05). Conclusion: Zoledronic acid significantly reduced SRE rate in cancer pts with bone metastasis by 30%, increased follow-up duration by almost 3 months, doubled time to 1st SRE, delayed time to 2nd SRE, with its label dose of 4 mg every 3 to 4 weeks achieving the best outcome. No significant financial relationships to disclose.