258P Cost-effectiveness of neoadjuvant pembrolizumab plus chemotherapy followed by adjuvant pembrolizumab for high-risk early-stage triple-negative breast cancer in Colombia

In Colombia, 15,509 new cases of breast cancer (BC) were diagnosed in 2020. Furthermore, BC was the leading cause of cancer deaths. Triple-negative breast cancer (TNBC) is an aggressive subtype that represents 15-20% of BC. The KEYNOTE-522 (KN522) trial showed that neoadjuvant pembrolizumab + chemotherapy followed by adjuvant pembrolizumab significantly improved pathological complete response and event-free survival when compared to neoadjuvant placebo + chemotherapy followed by adjuvant placebo in patients with high-risk early stage TNBC (eTNBC). This study evaluated the cost-effectiveness of neoadjuvant pembrolizumab + chemotherapy [paclitaxel + carboplatin followed by anthracycline + cyclophosphamide] plus adjuvant pembrolizumab versus neoadjuvant chemotherapy in high-risk eTNBC, from a third payer perspective in Colombia. A Markov cohort model was developed with four mutually exclusive health states: event-free, locoregional recurrence, distant metastasis, and death, to simulate patients’ lifetime disease course based on the efficacy and safety data from KN522. Outcomes and costs were discounted at 3% annually. Time on treatment was estimated using observed Kaplan-Meier curves from KN522. Utility inputs were derived from EuroQoL-five-dimension questionnaire in KN522. Costs for initial and subsequent therapies, disease and adverse events management, and terminal care were estimated using drug and healthcare public lists prices of Colombia. Over a 51-year time horizon, patients receiving pembrolizumab + chemotherapy accrued an additional 2.39 life-years (LYs) and 2.19 quality-adjusted life-years (QALYs) compared to neoadjuvant chemotherapy. The resulting incremental cost-effectiveness ratios (ICER) were COP 65,159,259/LY and COP 71,172,546/QALY, which were lower than the willingness-to-pay threshold of COP 85,093,272 in Colombia (based on 3-GDP per capita). Neoadjuvant pembrolizumab + chemotherapy followed by adjuvant pembrolizumab is a cost-effective treatment versus neoadjuvant chemotherapy for high-risk eTNBC in Colombia, constituting a novel and key therapy option for those patients.