Cost-effectiveness analysis of trastuzumab deruxtecan versus ramucirumab plus paclitaxel as second-line treatment for HER2-positive metastatic gastric cancer or gastroesophageal junction adenocarcinoma.

Background: Trastuzumab Deruxtecan (T-DXd) regimen has demonstrated substantial antitumor activity in the treatment of HER2-positive Metastatic Gastric Cancer (GC) or Gastroesophageal junction adenocarcinoma (GEJA). However, the cost-effectiveness of this regimen in this patient population remains uncertain, particularly within the Chinese healthcare system context. Objective: This study aimed to assess the cost-effectiveness of T-DXd regimen compared with ramucirumab plus paclitaxel regimen as second-line treatment for patients with HER2-positive advanced GC or GEJA, from the perspective of the Chinese healthcare system. Methods: A partitioned survival model was developed to project the disease progression. Data for overall survival (OS) and progression-free survival (PFS) were extracted from the DESTINY-Gastric04 trial and were extrapolated to project long-term survival outcomes. Direct medical costs and utility values were gathered. The main outcome measures, including the cost, utility, and incremental cost-utility ratio (ICUR), were used to determine the cost-effectiveness of the T-DXd regimen. Sensitivity analyses, including one-way sensitivity analysis (OWSA) and probabilistic sensitivity analysis (PSA), were performed to evaluate the robustness of the findings. Results: The base-case analysis revealed that the ICUR for T-DXd regimen was ¥$607,788.5 per quality-adjusted life year (QALY) compared to the ramucirumab plus paclitaxel regimen. OWSA showed that the ICUR was sensitive to the cost of subsequent treatment, weight and unit price of the two drugs. Results from the PSA indicated that T-DXd regimen had a probability of cost-effectiveness, at 4.3%. In contrast, ramucirumab plus paclitaxel regimen demonstrated a high likelihood of being cost-effective, with a 95.7% probability. Conclusion: In conclusion, from the perspective of the Chinese healthcare system, T-DXd was not cost-effective compared with the ramucirumab plus paclitaxel regimen for HER2-positive metastatic GC or GEJA under trial-based post-progression treatment patterns. However, when subsequent therapy in both arms is standardized to a common regimen and costs are limited to ¥28,053 per cycle, T-DXd will become the more cost-effective option. When only pre-progression outcomes were considered, T-DXd was associated with lower costs and greater survival benefits.