Cost-effectiveness of Pembrolizumab in Combination with Chemotherapy as Neoadjuvant Treatment and Continued as a Single Agent Adjuvant Treatment for High-Risk Early-Stage Triple-Negative Breast Cancer in Hong Kong.

Introduction: The phase III randomized KEYNOTE-522 trial demonstrated that pembrolizumab in combination with chemotherapy as neoadjuvant treatment followed by adjuvant pembrolizumab (pembrolizumab + chemotherapy) provided significant improvements in event-free survival (EFS) and overall survival (OS) for patients with high-risk early-stage triple-negative breast cancer (eTNBC). The objective was to assess the cost-effectiveness of pembrolizumab + chemotherapy compared to neoadjuvant chemotherapy alone (chemotherapy) in patients with high-risk eTNBC from a Hong Kong third-party payer perspective.

Methods: A multistate transition model with four health states (event-free), locoregional recurrence, distant metastases, and death) was developed to assess the lifetime medical costs and health outcomes (3% annual discount), along with incremental cost-effectiveness ratios (ICERs) using efficacy and safety data from the KEYNOTE-522 trial. The health state utilities were derived from KEYNOTE-522 Euro-QoL-five-dimension five-level questionnaire (EQ-5D-5L) data. Costs were expressed in 2022 Hong Kong dollars (HKD). Scenario and sensitivity analyses were performed to assess the robustness of results.

Results: Over a 32-year time horizon, base case results showed that pembrolizumab + chemotherapy was associated with a 3.42 year longer EFS and expected gains of 3.05 life years (LYs) and 2.45 quality-adjusted life years (QALYs) compared to chemotherapy. The resultant ICERs were HKD 135,200 per QALY gained and HKD 108,463 per LY gained, which were lower than the World Health Organization (WHO) cost-effectiveness threshold of three times gross domestic product (GDP) per capita for Hong Kong of HKD 1,171,308 per QALY. The one-way sensitivity analyses (OWSA) and probabilistic sensitivity analysis (PSA) showed the results were robust across various inputs and alternative scenarios.

Conclusion: On the basis of the analysis conducted for a 56-year-old cohort with high-risk eTNBC and assumptions in the model, pembrolizumab + chemotherapy represents a cost-effective proposition (as the ICER is approximately 35% of the GDP per capita in Hong Kong) for patients with high-risk eTNBC in Hong Kong.