151 Background: Pathologic fractures (PF) are a common and expensive-to-treat skeletal-related event (SRE), which affect over two-thirds of metastatic breast cancer (MBC) patients, and cost $26,936 (2009 US dollars) per event on average for inpatient treatment. In a phase III trial ( NCT20050136 ), MBC patients randomized to denosumab (Dmab; n=1,026) demonstrated longer time to SRE, but comparable rates of survival and disease progression relative to those randomized to zoledronic acid (ZOL; n=1,020). We calculated the number needed to treat (NNT) to avoid one PF and the treatment cost per PF avoided with Dmab vs. ZOL in MBC patients. Methods: Phase III trial results from the Dmab product label were used to determine the rate of PFs and SREs in MBC patients treated with Dmab vs. ZOL. Treatment cost included only the wholesale acquisition cost of Dmab and ZOL, and assumed 12 months of treatment. The NNT calculated the number of patients who would need to be treated with Dmab vs. ZOL to avoid one additional PF. Sensitivity analyses included expanding the treatment outcome from PFs to SREs and adding drug administration costs for Dmab and ZOL, and, renal monitoring costs only for ZOL. Results: Based on the estimated differences in PF risk of 2.7%, 37.4 patients would need to be treated with Dmab vs. ZOL to avoid one additional PF, resulting in a treatment cost per PF avoided of $346,911. The lower 95% confidence limit for the cost per PF avoided with Dmab vs. ZOL was $148,114, which is significantly greater than the mean inpatient cost of treating a PF event. Including drug administration and renal monitoring costs led to a cost per PF avoided of $323,069. Expanding the treatment outcome from PFs to SREs showed that 17.3 patients would need to be treated with Dmab vs. ZOL to avoid one additional SRE (95% CI: 10.2 to 59.7; absolute risk reduction 5.8%), resulting in a treatment cost of $160,595 per SRE avoided. Conclusions: PFs have a debilitating effect on patients, and treatment with Dmab compared to ZOL was associated with a treatment cost per PF avoided that exceeded 12 times the mean inpatient cost of a PF. Decision makers need to consider the high costs associated with Dmab prior to formulary inclusion.
Effects on bone resorption markers of continuing pamidronate or switching to zoledronic acid in patients with high risk bone metastases from breast cancer