An economic evaluation of anastrozole versus tamoxifen as adjuvant therapy in postmenopausal women with early breast cancer (EBC) from a US healthcare perspective

Abstract

590 Background: Results from the ATAC trial (Lancet 2002;359:2131) at a median follow-up of 33 months, indicated that anastrozole (n=3125) was superior to tamoxifen (n=3116) for disease free survival (DFS) in the adjuvant treatment of postmenopausal women with hormone receptor-positive (HR+) early breast cancer. Updated data (median follow-up 47.2 months for efficacy) confirmed these findings (Cancer 2003;98:1802). Using the updated data, the incremental cost effectiveness ratio (ICER) per life year gained (LYG) for managing this group was calculated for anastrozole vs tamoxifen from the US healthcare perspective. Methods: A probabilistic Markov model was developed using updated ATAC data to project outcomes for anastrozole and tamoxifen to 25 yrs by extrapolating pooled Kaplan-Meier curves using parametric statistical methods. It was assumed that recurrence rates after the maximum 5 yr treatment period would be equivalent in anastrozole and tamoxifen groups, a conservative approach. General mortality data were from US Census 2000. Resource utilization data was obtained from published literature and structured interviews with 9 US oncologists. Drug costs were based on average wholesale price and generic cost of tamoxifen. Other unit costs (2002 US$) from standard national sources and literature were used. Costs and benefits were discounted at 3%. Sensitivity analyses were conducted. Results: In a cohort of 1000 patients modeled over 25 yrs, anastrozole was estimated to lead to 145 discounted life years gained at an additional cost of $3.6 million. The discounted ICER of anastrozole compared to tamoxifen was estimated to be $25,169/LYG (95% CI $5,925–$48,593). Acceptability curves showed that the estimated cost/LYG at 25 yrs was below $50,000 with a probability >90%. The result compared favorably with commonly accepted thresholds for cost-effectiveness and was robust to all parameters, including AEs, tested in sensitivity analysis. Conclusions: Anastrozole is a cost-effective alternative to tamoxifen for the adjuvant treatment of postmenopausal women with HR+ early breast cancer. Author Disclosure Employment or Leadership Consultant or Advisory Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration AstraZeneca AstraZeneca