Abstract
BACKGROUND: Combining Trastuzumab with chemotherapy for HER2-positive gastric cancer shows treatment promise but may raise costs. We aimed to evaluate the cost-effectiveness of combining Trastuzumab with chemotherapy for HER2-positive gastric cancer treatment in Iran. METHODS: We employed a partitioned survival model (PSM) to evaluate the cost-effectiveness of trastuzumab plus chemotherapy versus chemotherapy alone. The PSM framework included three distinct health states: progression-free, post-progression, and death. Clinical data, including overall survival and progression-free survival rates, were derived from the ToGA trial, a randomized controlled study. A bottom-up approach was used to calculate costs by considering drug costs, adverse event management costs and other disease management costs separately for the progression-free and post-progression states. The analysis was conducted from the Iranian healthcare system's perspective, considering direct medical costs. We performed a cost-effectiveness analysis to determine the optimal strategy by comparing the incremental cost-effectiveness ratio (ICER) to Iran's cost-effectiveness threshold, set at one to three times the GDP per capita. Additionally, we conducted sensitivity analyses to assess the robustness of our findings. RESULTS: Both FOLFOX-based regimens were strongly dominated. In comparison, the CAPOX regimen cost $2,811.11 for 0.75 QALYs. Adding Trastuzumab to CAPOX increased the cost to $6,128 and improved effectiveness to 0.92 QALYs, resulting in an ICER of $19,089.94 per QALY, which is between 2 and 3 times the GDP per capita in 2022. CONCLUSION: The addition of trastuzumab to chemotherapy regimens improved clinical outcomes in HER2-positive gastric cancer patients. From an economic perspective, the CAPOX regimen is the most cost-effective option when considering a cost-effectiveness threshold of up to two times Iran's GDP per capita. However, when the threshold increases to three times the GDP per capita, the CAPOX + Trastuzumab regimen becomes the preferred choice. These findings provide valuable insights for healthcare policymakers in Iran.