OBJECTIVES: To evaluate cost-effectiveness of pembrolizumab plus chemotherapies for first-line treatment of locally advanced unresectable or metastatic triple negative breast cancer (mTNBC), from the French healthcare system perspective.

METHODS: A three-state partitioned survival model (pre-progression, post-progression and death) was developed to estimate costs, effectiveness, and incremental cost-effectiveness ratio (ICER) of pembrolizumab + chemotherapies vs chemotherapies. Comparison with bevacizumab + paclitaxel was included in exploratory analyses only due to lack of published overall survival data in mTNBC population. Clinical and quality of life data were derived from the phase 3 study KEYNOTE-355. Progression-free survival, overall survival and time on treatment were extrapolated over a 10-year time horizon based on parametric functions. EQ-5D-3L data were converted to French population-based utilities using the French value set. Only direct medical costs were considered, based on public sources. Costs and health outcomes were discounted at 2.5% per year. ICER was calculated as cost per quality-adjusted life year (QALY) gained and per life year gained (LYG). Deterministic and probabilistic sensitivity analyses and scenarios analyses were performed to assess robustness of results.

RESULTS: The model projected that pembrolizumab + chemotherapies is associated with discounted 0.67 LYG and 0.52 additional QALY vs chemotherapies as well as incremental costs of 71,660€. ICERs were 138,765€/QALY and 106,275€/LYG respectively. Sensitivity analyses led to an ICER varying from 115,522€/QALY to 205,277€/QALY. The willingness-to-pay threshold should reach 200,000 €/QALY, to have more than 80% probability of being cost-effective. Exploratory analyses showed bevacizumab + paclitaxel remained dominated under all plausible scenarios considered.

CONCLUSIONS: Combining pembrolizumab with chemotherapies improves life expectancy and appears cost-effective versus chemotherapies alone for first-line treatment of mTNBC in France, assuming a WTP under 200,000€/QALY.