Cost-effectiveness analysis of anastrozole versus tamoxifen as primary adjuvant therapy for postmenopausal women with early breast cancer: a US healthcare system perspective. The 5-year completed treatment analysis of the ATAC ('Arimidex', Tamoxifen Alone or in Combination) trial.

Background: This study evaluated the cost-effectiveness of anastrozole versus generic tamoxifen for primary adjuvant treatment of postmenopausal women with hormone receptor-positive (HR+) early breast cancer (EBC), from a US healthcare perspective.

Methods: A probabilistic Markov model was developed using the 5-year completed treatment analysis of the ATAC ('Arimidex', Tamoxifen Alone or in Combination) trial (ISRCTN 18233230) to project outcomes for anastrozole and tamoxifen to 25 years. Resource utilization data were obtained primarily from published literature and a physician survey (including expert opinion from ATAC Steering Committee members). Drug costs were taken from published wholesale acquisition costs (anastrozole $6.56/day, generic tamoxifen $1.33/day). Other unit costs ($US 2003-4) were from standard sources. Utility estimates of relevant health states, used to compute quality-adjusted life-years (QALYs), were collected using the standard gamble technique in a cross-sectional sample of 44 patients. Costs and benefits were discounted 3% annually.

Results: In a cohort of 1000 postmenopausal women with HR+ EBC, the model showed anastrozole treatment (versus tamoxifen) would lead to 257 QALYs gained (0.26 QALYs gained per patient), at an additional cost of $5.21 million over 25 years ($5,212 per patient). The estimated incremental cost-effectiveness ratio (ICER) of anastrozole compared with tamoxifen was $20,246 per QALY gained ($23,541 per life-year gained). Cost-effectiveness acceptability curves indicated a >90% probability that the cost per QALY gained with anastrozole would be <$50,000. Results were robust in a sensitivity analysis.

Conclusion: Anastrozole is a cost-effective alternative to tamoxifen for the primary adjuvant treatment of postmenopausal women with HR+ EBC.