Cost-effectiveness analysis of trastuzumab monotherapy versus adjuvant chemotherapy plus trastuzumab in elderly patients with HER2-positive early breast cancer

Background: In elderly patients with human epidermal growth factor 2-positive breast cancer, adjuvant chemotherapy was associated with decreased quality of life, with relatively small benefits for prognosis. We examined the cost-effectiveness of trastuzumab monotherapy versus adjuvant chemotherapy plus trastuzumab in elderly patients with human epidermal growth factor 2-positive breast cancer. Methods: A Markov model was developed to evaluate the costs and benefits of trastuzumab monotherapy over adjuvant chemotherapy plus trastuzumab for elderly patients with human epidermal growth factor 2-positive breast cancer. We built the model with a yearly cycle over a 20-year time horizon and five health states: disease-free, relapse, post-relapse, metastasis and death. The parameters in the model were based on a previous randomized controlled trial and a nationwide administrative database in Japan. The incremental cost-effectiveness ratio, expressed as Japanese yen per the quality-adjusted life-years, was estimated from the perspective of health care payers. One-way deterministic sensitivity analysis and probabilistic sensitivity analysis with Monte-Carlo simulations of 10 000 samples were conducted. Results: The incremental cost-effectiveness ratio of trastuzumab monotherapy over adjuvant chemotherapy plus trastuzumab was similar to 1.8 million Japanese yen /quality-adjusted life-year. The one-way deterministic sensitivity analysis showed that transition probability from disease-free to metastasis status and cost of metastasis status had the greatest influence on the incremental cost-effectiveness ratio. More than half the estimates in the probabilistic sensitivity analysis were located below a threshold of willingness-to-pay of 5 million Japanese yen /quality-adjusted life-year. Conclusion: In this first comparative cost-effectiveness analysis of adjuvant chemotherapy plus trastuzumab versus trastuzumab monotherapy in the elderly, the latter was found favorable for elderly patients with human epidermal growth factor 2-positive breast cancer.