RESUMO
PURPOSE: This study aims to evaluate the cost-effectiveness of two aromatase inhibitors for the adjuvant treatment of women with postmenopausal hormone receptor positive early breast cancer, and to find the most reasonable treatment option when the population is stratified by the nodal status. METHODS: A Markov model was developed with defining six Markov states based on breast cancer progression. The annual probabilities of recurrence by adjuvant treatment (anastrozole, letrozole, and tamoxifen) were estimated from the published studies in the overall population and in the node negative and node positive groups. The costs of the defined breast cancer events were measured by the micro-costing method based on the 2009 National Health Insurance Fee Schedule and the third Clinical Guideline of Breast Cancer Treatment. Anastrozole and letrozole were compared with tamoxifen respectively, using the same Markov model. The incremental cost-effectiveness ratios for the overall population and each subgroup were estimated. RESULTS: Anastrozole was more effective and costly than tamoxifen with anastrozole costing an additional Korean Won (KRW) 22,461,689 per quality-adjusted life year (QALY). Letrozole showed a similar incremental cost of KRW 21,004,142 per QALY. In the node negative group, anastrozole was the most cost-effective with an incremental cost of KRW 19,717,770 per QALY, while letrozole was the most cost-effective with an incremental cost of KRW 8,150,512 per QALY for the node positive group. The sensitivity analysis showed that these results were robust. CONCLUSION: The subgroup analysis clearly demonstrated which treatment was superior among the aromatase inhibitors in terms of the cost-effectiveness. Such a finding was not confirmed for the case of the overall population. The implication of this study is that the decision makers should be careful when generalizing the cost-effectiveness results. The stratified analysis in this context may help reach a reasonable decision for allocating medical resources.