Irinotecan as the key chemotherapeutic agent in second-line treatment of metastatic gastric cancer after failure of first-line S-1 or S-1/CDDP therapy

Background: S-1, an oral fluoropyrimidine, is one of the standard chemotherapeutic agents for the treatment of metastatic gastric cancer (MGC). However, the most effective second-line regimen after failure of treatment with first-line agents such as S-1 is yet to be determined. The aim of this study was to investigate the various second-line chemotherapy regimens in MGC patients. Methods: We retrospectively studied patients with MGC who received second-line treatment after failure of the first-line S-1 or S-1/cisplatin treatment. The overall survival times with each second-line regimen were determined using the Kaplan-Meier method, and the effect on overall survival was analyzed using Cox regression analysis. Results: The median survival time for all patients was 14.2 months (95% confidence interval (CI): 12.88-15.43 months) with a 1-year survival rate of 60.4%. Kaplan-Meier analysis revealed that the second-line regimens containing irinotecan significantly improved the median survival time as compared to regimens without irinotecan (median survival time: 16.5 and 13.8 months, respectively). Cox regression analysis showed that irinotecan-containing regimens were associated with improved overall survival (hazard ratio: 0.165; 95% CI: 0.041-0.665). Conclusion: The use of irinotecan-containing regimens as second-line chemotherapy after failure of first-line S-1 therapy may be beneficial for MGC patients.