Cost-utility of adjuvant zoledronic acid in patients with breast cancer and low estrogen levels

Background Adjuvant zoledronic acid (ZA) appears to improve disease-free survival (DFS) in women with early-stage breast cancer and low levels of estrogen (LLE) because of induced or natural menopause. Characterizing the cost-utility (CU) of this therapy could help to determine its role in clinical practice. Methods Using the perspective of the Canadian health care system, we examined the CU of adjuvant endocrine therapy with or without ZA in women with early-stage endocrine-sensitive breast cancer and LLE. A Markov model was used to compute the cumulative costs in Canadian dollars and the quality-adjusted life-years (QALYS) gained from each adjuvant strategy, discounted at a rate of 5% annually. The model incorporated the DFS and fracture benefits of adjuvant ZA. Probabilistic and one-way sensitivity analyses were conducted to examine key model parameters. Results Compared with a no-ZA strategy, adjuvant ZA in the induced and natural menopause groups was associated with, respectively, $7,825 and $7,789 in incremental costs and 0.46 and 0.34 in QALY gains for CU ratios of $17,007 and $23,093 per QALY gained. In one-way sensitivity analyses, the results were most sensitive to changes in the ZA DFS benefit. Probabilistic sensitivity analysis suggested a 100% probability of adjuvant ZA being a cost-effective strategy at a threshold of $100,000 per QALY gained. Conclusions Based on available data, adjuvant ZA appears to be a cost-effective strategy in women with endocrine-sensitive breast cancer and LLE, having CU ratios well below accepted thresholds.