Pharmacoeconomic analysis of adjuvant therapy with exemestane, anastrozole, letrozole or tamoxifen in postmenopausal women with operable and estrogen receptor-positive breast cancer.

OBJECTIVE: To compare the efficiency of adjuvant therapy with aromatase inhibitors or with tamoxifen in postmenopausal women with operable breast cancer and positive estrogen receptors.

MATERIAL AND METHODS: A cost-utility analysis was performed based on a Markov model, from the Spanish National Health Care System perspective, comparing the treatment with exemestane (EXE: 25 mg/day) or tamoxifen (TAM: 20 mg/day) after 2-3 years of monotherapy with TAM; anastrozole (ANA, 1 mg/day) or TAM (20 mg/day) without previous TAM therapy; and letrozole (LET: 2.5 mg/day) or placebo after 5 years of monotherapy with TAM. The follow-up of a hypothetical cohort of women starting treatment at 63 years of age was simulated during 10 and 20 years. The probabilities of transition between health states and quality adjusted life years (QALYs) were obtained from the literature, and the unit costs (euro corresponding to 2004) from a Spanish database.

RESULTS: After 10 and 20 years of follow-up, more QALYs per patient would be gained with the EXE scheme (0.230-0.286 and 0.566-0.708, respectively) than with ANA (0.114 and 0.285) and LET (0.176 and 0.474). The cost of gaining one QALY was lower with the EXE scheme (50,801-62,522 euro and 28,849- 35,371 euro, respectively) than with ANA (104,272 euro and 62,477 euro) and LET (91,210 euro and 49,460 euro). The result was stable for the cost per life-year gained (LYG) and in the sensitivity analysis.

CONCLUSIONS: The EXE scheme after TAM is more cost-effective than the ANA and LET schemes.