Cost-effectiveness of pembrolizumab plus trastuzumab and chemotherapy for HER2-positive gastric or gastro-oesophageal junction adenocarcinoma.

To investigate the cost-effectiveness of pembrolizumab in combination with trastuzumab and chemotherapy as a first-line treatment for HER2-positive gastric or gastro-esophageal junction adenocarcinoma from the perspective of the U.S. and Chinese healthcare systems. In this economic evaluation, a Markov model is constructed from the perspective of the U.S. and Chinese healthcare systems. The survival data were derived from the clinical trial (KEYNOTE-811), while cost data generated during treatment were sourced from pricing, databases, and expert consultations in local hospitals. Total costs, quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) were estimated in US dollars. Its robustness is evaluated by deterministic and probabilistic sensitivity analysis. Basic case analysis showed that pembrolizumab in combination with trastuzumab and chemotherapy, as a new treatment strategy, had higher cost-effectiveness compared with trastuzumab plus chemotherapy treatment, with willingness-to-pay (WTP) thresholds set at $150,000 per QALY for the United States population and $40,334.05 per QALY for the China population The ICER was $88,507.57 per QALY in the United States and $22,461.22 per QALY in China, both below the respective thresholds. Sensitivity analysis demonstrated that the results were robust. From the perspective of the U.S. and Chinese medical and health services, pembrolizumab in combination with trastuzumab and chemotherapy is more cost-effective than chemotherapy in the treatment of HER2-positive gastric or gastro-esophageal junction adenocarcinoma patients. Within the context of China's health technology assessment and National Reimbursement Drug List negotiation framework, the ICER below the three-times-GDP threshold suggests preliminary economic feasibility at current price levels, indicating that the regimen may warrant consideration for reimbursement decisions, subject to further budget impact analysis and price negotiation. The evidence-based pricing strategies provided in this study may be helpful for decision makers and clinicians to make the best decisions in general clinical practice. More evidence on budgetary impact and patient affordability is needed.