Potential clinical and economic impact of switching U.S. women to exemestane following 2–3 years of therapy with tamoxifen for early breast cancer

Abstract

6109 Background: Switching postmenopausal women with early breast cancer to exemestane after 2–3 years of tamoxifen therapy has been reported to increase disease-free survival. However, the potential impact of this management strategy on the U.S. health-care system is unknown. The objective of this study was to estimate the 10-year clinical and economic consequences that would accrue if all eligible U.S. patients in 2006 were switched from tamoxifen to exemestane. Methods: A Markov model with a 10-year time horizon was used to predict patients’ transitions across various health states based on treatment strategy (continuing tamoxifen versus switching to exemestane), breast cancer status (no recurrence, local or distant recurrence, contralateral breast cancer), and other related health events (osteoporosis, endometrial cancer, death). Disease- and treatment-related events were estimated using data from the Intergroup Exemestane Study (IES); survival and medical-care costs by type of recurrence were estimated using SEER-Medicare data and published literature. The switch-eligible cohort was defined to be consistent with IES selection criteria and its size in 2006 estimated based on SEER-Medicare and market research data. Costs incurred in future years were discounted at 3% annually. Results: We estimate that 71,800 U.S. women would be eligible to switch from tamoxifen to exemestane in 2006. Doing so would be expected to prevent 3,000 cases of recurrence (21,100 vs 24,100) and 2,000 breast cancer deaths (12,800 vs 14,800) over 10 years. The net budgetary impact over 10 years is projected to be $320M ($992M vs $672M), reflecting a $336M increase in costs of adjuvant hormonal therapy ($500M vs $164M), a $32.1M increase in costs of monitoring and treatment of adverse events ($73.7M vs. $41.6M), and a $47.4M reduction in recurrence-related treatment costs ($419M vs $466M). Conclusion: Switching all eligible U.S. breast cancer patients from tamoxifen to exemestane in 2006 would increase medical-care costs by $4,460 per patient but reduce breast cancer recurrences by 12% and breast cancer deaths by 14% over 10 years. [Table: see text]