Comparing cost/utility of giving an aromatase inhibitor as monotherapy for 5 years versus sequential administration following 2–3 or 5 years of tamoxifen as adjuvant treatment for postmenopausal breast cancer

Background: Several studies have shown aromatase inhibitors administered as monotherapy or sequentially to tamoxifen to improve relapse-free survival in postmenopausal women with early breast cancer. Any difference in cost/utility between the strategies may be of importance to therapy selection. Methods: Cost/utility was compared between the different regimens based on the theoretical assumption that costs, benefits and side-effects were similar for each drug and independent of whether it was administered as monotherapy or sequentially. Results: Tamoxifen for 2–3 years followed by an aromatase inhibitor for 3 or 2 years provided the lowest cost/quality-adjusted life years (QALY) estimates, while administration of an aromatase inhibitor subsequent to 5 years on tamoxifen provided the highest values. The difference between strategies increased with patient age. Cost/QALY estimates were sensitive to an increase in hip fracture risk and to cost reductions due to relapse prevention. Adding oral bisphosphonates increased costs moderately. Conclusions: While tamoxifen for 2–3 years followed by an aromatase inhibitor provided the lowest cost/QALY estimates, a further improvement of relapse-free survival of 1% if the aromatase inhibitor is given upfront provides an acceptable cost/QALY. In contrast, additional benefits achieved by administering an aromatase inhibitor subsequent to 5 years of tamoxifen provided unacceptable costs.