OBJECTIVES: This analysis aimed to evaluate the cost effectiveness of pembrolizumab in combination with chemotherapy (paclitaxel, nab-paclitaxel or gemcitabine+carboplatin) vs chemotherapy as first-line treatment in patients with locally recurrent unresectable or metastatic triple negative breast cancer (mTNBC) whose tumors express programmed death ligand-1 (PD-L1) (combined positive score (CPS) ≥10), from a US third-party public healthcare payer perspective.

METHODS: A partitioned-survival model was developed using efficacy and safety data from the KEYNOTE-355 randomized clinical trial and projected over 20 years. Quality-adjusted life-years (QALYs) were calculated based on EuroQoL-5 Dimensions (EQ-5D) utility data collected in the trial. Costs ($US, year 2021 values) for drug acquisition/administration, adverse events and disease management were included. Costs and outcomes were discounted at 3% per year. A series of deterministic and probabilistic sensitivity analyses were performed to test the robustness of the results.

RESULTS: In the base-case scenario, pembrolizumab combined with chemotherapy resulted in an expected gain of 0.84 life-years (LYs) and 0.70 QALYs and an incremental cost of $US127,706 compared with chemotherapy. The incremental cost per QALY gain was $US182,732/QALY and the incremental cost per LY gain was $US152,289/LY.

CONCLUSIONS: Pembrolizumab combined with chemotherapy is projected to be a cost-effective option compared with chemotherapy alone as first-line treatment in mTNBC with PD-L1 CPS≥10 from a third-party US public payer perspective, based on the WHO willing-to-pay threshold of 3-times GDP per capita.