Comparison of the cost per distant disease-free year gained for upfront letrozole or anastrozole, or switched exemestane compared to tamoxifen for early breast cancer in hormone receptor-positive postmenopausal women: The UK perspective

Abstract

557 Background: Due to subsequent poor prognosis, prevention of distant recurrence (DR) is a primary aim of adjuvant hormonal therapy for early breast cancer. Compared to 5 years TAM in hormone receptor positive (HR+) postmenopausal women, DR relative risks are 0.73 (95% CI 0.6 - 0.88) for 5 years letrozole (LET), 0.84 (95% CI 0.7 - 1.0) for 5 years anastrozole (ANA), 0.73 (95% CI 0.59 - 0.9) for 2–3yrs exemestane after 2–3 years (EXE/TAM). This analysis evaluates the incremental cost per distant disease free year gained from a UK NHS perspective of LET, ANA, EXE/TAM versus 5 years TAM using the same health economic model. Methods: A Markov model described pathways through relevant health states over the remaining lifetime of a cohort of HR+ women aged 61 yrs. Probabilities of breast cancer events (contralateral; locoregional; soft tissue, bone, and visceral metastases) adverse events (endometrial cancer, hip and other fractures, cardiovascular disease, thromboembolic events, and arthralgia) were based on the latest early breast cancer overview, published results of the BIG 1–98, ATAC, and IES trials, and UK population-based studies as appropriate. Conservatively, no carry-over effect was assumed for the AIs after therapy discontinuation. Costs (2005 UK£) of breast-cancer care were obtained from a primary costing study in Scotland, and treatment costs for AEs were obtained from published studies. Costs and DR-free years were discounted at 3.5% annually. Results: The mean durations of DDFS were estimated to be 12.81, 12.66, 12.57, and 12.35 years for LET, ANA, TAM/EXE, and TAM, respectively. The incremental cost per distant disease free year gained of LET vs TAM is £10,379 (95% CI £5,286-£17,818), of ANA vs TAM is £11,428 (95% CI £5,071- £48,856), and of TAM/EXE vs TAM alone is £11,020 (95% CI £4,820-£36,947). Conclusion: Compared to 5 years TAM, adjuvant treatment of postmenopausal HR+ women with an AI is a cost-effective use of UK NHS resources. Based on the mean results, LET appears to be the most cost-effective of the three AIs, despite its higher acquisition cost compared to ANA in the UK, though the confidence intervals are wide. [Table: see text]