Cost-effectiveness of extended adjuvant letrozole therapy after 5 years of adjuvant tamoxifen therapy in postmenopausal women with early-stage breast cancer.

OBJECTIVE To estimate the cost-effectiveness of extended adjuvant letrozole in postmenopausal women with early breast cancer and estrogen or progesterone receptor-positive tumors who had completed 5 years of adjuvant tamoxifen. STUDY DESIGN Cost-effectiveness analysis using a Markov model. METHODS Using a Markov model, we estimated the incremental cost per quality-adjusted life-year (QALY) gained with extended adjuvant letrozole vs no extended adjuvant therapy. Probabilities of breast cancer recurrence or new contralateral tumor adverse effects and death were estimated using data from the MA.17 study and other secondary sources. Costs (in 2004 US dollars) and quality-of-life effects (utilities) of breast cancer events and adverse effects were derived from the literature. RESULTS In base-case analyses, extended adjuvant letrozole vs no extended adjuvant therapy results in an expected gain of 0.34 QALYs per patient (13.62 vs 13.28 QALYs), at an additional lifetime cost of 9699 dollars per patient (55,254 dollars vs 45,555 dollars). The incremental cost per QALY gained with letrozole is 28,728 dollars. Cost-effectiveness is sensitive to the assumed reduction in risk of breast cancer events with letrozole but is insensitive to the risks, costs, and quality-of-life effects of osteoporosis and hip fracture. Cost-effectiveness is less than 100,000 dollars per QALY for node-positive patients younger than 81 years and for node-negative patients younger than 73 years. CONCLUSION For postmenopausal women with early breast cancer who have completed 5 years of adjuvant tamoxifen, the cost-effectiveness of extended adjuvant letrozole is within the range of other generally accepted medical interventions in the United States.