Cost-effectiveness of letrozole versus tamoxifen as initial adjuvant therapy in postmenopausal women with hormone-receptor positive early breast cancer from a Canadian perspective

Background

In the primary core analysis of BIG 1–98, a randomized, double-blind trial comparing 5 years of initial adjuvant therapy with letrozole versus tamoxifen in postmenopausal women with hormone receptor-positive (HR+) early breast cancer, letrozole significantly improved disease-free survival by 19% and reduced the risk of breast cancer recurrence by 28% and distant recurrence by 27%.
Methods

A Markov model was used to estimate the incremental cost per quality-adjusted life year (QALY) gained with 5 years of initial adjuvant therapy with letrozole versus tamoxifen from a Canadian healthcare system perspective. Probabilities of recurrence and side effects for tamoxifen were based on published results of BIG 1–98 and other published population-based studies. Corresponding probabilities for letrozole were calculated by multiplying probabilities for tamoxifen by estimated relative risks for letrozole versus tamoxifen from BIG 1–98. Other probabilities, costs of breast-cancer care and treatment of side effects, and health-state utilities were obtained from published studies. Costs and QALYs were estimated over the lifetime of a cohort of postmenopausal women with HR+ early breast cancer, aged 60 years at initiation of therapy, and discounted at 5% annually.
Results

Compared with tamoxifen, letrozole yields an additional 0.368 life-years (12.453 vs. 12.086) and 0.343 QALYs (11.582 vs. 11.239). These benefits are obtained at an additional cost of $Can 8,110 ($Can 30,819 vs. $Can 22,709). Cost per QALY gained for letrozole versus tamoxifen is $Can 23,662 (95% CI $Can 15,667–$Can 52,014).
Conclusion

In postmenopausal women with HR+ early breast cancer, initial adjuvant treatment with letrozole is cost-effective from the Canadian healthcare system perspective.