10577 Background: The BIG 1–98 and ATAC studies demonstrated that, in postmenopausal women with hormone receptor positive (HR+) early breast cancer, 5 years of initial adjuvant therapy with the aromatase inhibitors (AIs) letrozole (LET) or anastrozole (ANA) is superior to tamoxifen (TAM). The cost-effectiveness TAM, LET, and ANA have not been previously evaluated using a consistent methodology. Methods: A Markov model was used to estimate the incremental cost per quality-adjusted life year (QALY) gained with initial adjuvant therapy with LET vs TAM, ANA vs TAM, and LET vs ANA in postmenopausal women with HR+ early stage breast cancer from the US healthcare system perspective. Probabilities of recurrence (including contralateral tumor) and adverse events (endometrial cancer, thromboembolism, fractures, hypercholesterolemia, MI, and stroke) for TAM were based primarily on published US population-based studies and trials of prophylactic TAM vs placebo. Corresponding probabilities for LET and ANA were calculated by multiplying probabilities for TAM by estimated relative risks of LET vs TAM and ANA vs TAM from the BIG 1–98 and ATAC trials respectively. Other probabilities, costs, and health-state utilities were obtained from published studies. Expected lifetime costs and QALYs were estimated for a cohort of HR+ postmenopausal women with early breast cancer, aged 61 years at therapy initiation and discounted at 3% annually. Probabilistic sensitivity analyses were conducted to assess precision of results. Results: Incremental cost per QALY gained for LET vs TAM is $33,536 (95% CI $20,409 to $70,566) and for ANA vs TAM is $38,967 (95% CI $23,826 to $81,904). Compared with ANA, LET is less costly ($9,647 vs $10,190) and gains more QALYs (0.29 vs 0.26), although differences in costs (95% CI -$1,669 to $671) and QALYs (95% CI -0.16 to 0.22) are not statistically significant. Conclusions: In postmenopausal women with HR+ early breast cancer, adjuvant therapy with either LET or ANA is cost-effective from a US healthcare system perspective. Although LET dominates ANA in our base-case analysis, definitive conclusions regarding the cost-effectiveness of LET vs ANA must await results of comparative clinical studies. [Table: see text]
PCN20 COST-EFFECTIVENESS ASSESSMENT FOR COLOMBIA OF LETROZOLE VS. TAMOXIFEN IN ADJUVANT TREATMENT OF HORMONE RECEPTOR-POSITIVE, POST-MENOPAUSAL EARLY BREAST CANCER WOMEN