Systematic Review of Economic Evaluations of Systemic Treatments for Advanced and Metastatic Gastric Cancer.

Background: Recent advances in the development of biomarker-directed therapy and immunotherapy, for advanced and metastatic gastric cancers, have the potential to improve survival and quality of life. Much attention has been directed towards second- and later-line treatments, and the landscape here is evolving rapidly. However, uncertainty in relative effectiveness, high costs and uncertainty in cost effectiveness represent challenges for decision makers.

Objective: To identify economic evaluations for the second-line or later-line treatment of advanced and metastatic gastric cancer. Also, to assess key criteria (including model assumptions, inputs and outcomes), reporting completeness and methodological quality to inform future cost-effectiveness evaluations.

Methods: A systematic literature search (from database inception to 5 March 2023) of EconLit via EBSCOhost, Cochrane Library (restricted to National Health Service [NHS] Economic Evaluation Database and Health Technology Assessment [HTA] Database), Embase, MEDLINE and of grey literature was conducted. This aimed to identify systemic treatments that align with National Comprehensive Cancer Network (NCCN) and European Society for Medical Oncology (ESMO) Clinical Practice Guidelines. Data were collected on key criteria and on reporting completeness and methodological quality. A narrative synthesis focussed on cost-effectiveness and cost-of-illness studies. Outcomes of interest included total and incremental costs and outcomes (life-years and quality-adjusted life-years), ratios of incremental costs per unit outcome and other summary cost and outcome measures. Also, for cost-effectiveness studies, reporting completeness and the methodological quality were assessed using the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) and the Philips Checklist, respectively.

Results: A total of 19 eligible economic evaluations were identified (cost-effectiveness studies [n = 15] and cost-of-illness studies [n = 4]). There was a general lack of consistency in the methodological approaches taken across studies. In the main, the cost-effectiveness studies indicated that the intervention under consideration was more effective and more costly than the comparator(s). However, most interventions were not cost effective. No studies were fully compliant with reporting-completeness and methodological-quality requirements. Given the lack of consistency in the approaches taken across cost-of-illness studies, outcomes could not be directly compared.

Conclusions: To our knowledge, this is the first published systematic literature review that has qualitatively synthesised economic evaluations for advanced and metastatic gastric cancer. There were differences in the approaches taken across the cost-effectiveness studies and the cost-of-illness studies. The conclusions of most of the cost-effectiveness studies were consistent despite identified differences in approaches. In the main, the interventions under consideration were not cost effective, presenting challenges to sustainability and affordability. We highlight a requirement for cost-effectiveness evaluations and for second-line or later-line treatments of advanced and metastatic gastric cancer that consider all relevant comparators and that are compliant with reporting-completeness and methodological-quality requirements. By addressing the methodological gaps identified here, future healthcare decision-making, within the context of this rapidly changing treatment landscape, would be better informed.

Prospero registration number: CRD42023405951.