Cost-effectiveness analysis of trastuzumab to treat HER2-positive advanced gastric cancer based on the randomised ToGA trial

BACKGROUND: We performed a cost-effectiveness analysis of trastuzumab plus chemotherapy for human epidermal growth factor type-2 (HER2)-positive advanced gastric cancer (GC) based on data obtained from the Trastuzumab for Gastric Cancer (ToGA) trial from a Japanese perspective. METHODS: The following Japanese and Korean populations of the ToGA trial were analysed to obtain mean overall and progression-free survival times: (1) all HER2-positive populations, (2) immunohistochemical (IHC) 2+/fluorescence in situ hybridisation (FISH)+ or IHC 3+ populations, and (3) IHC 3+ only population. The effect of trastuzumab treatment on mean survival time was estimated by fitting a Weibull parametric function. Costs were calculated from the perspective of health-care payer. Neither costs nor outcomes were discounted because of short life expectancy. RESULTS: In the base-case analysis, the incremental cost-effectiveness ratio was (1) JPY 12 million (€110 000) per quality-adjusted life year (QALY) gained and JPY 8.9 million (€81 000) per life-year gained (LYG) for all HER2-positive populations, (2) JPY 9.1 million (€83 000) per QALY gained and JPY 6.6 million (€60 000) per LYG for the IHC 2+/FISH+ or IHC 3+ population, and (3) JPY 6.1 million (€55 000) per QALY gained and JPY 4.3 million (€39 000) per LYG for the IHC 3+ population. CONCLUSION: Trastuzumab treatment for IHC 3+ populations is cost effective. Our analysis can find a cost-effective subgroup when advanced GC is treated by trastuzumab.