[Real World Impact of Immunotherapy in Patients with Unresectable Gastric Cancer].

[Objective]To clarify the effect of immunotherapy on unresectable gastric cancer. [Subjects and methods]The study included all 67 patients with gastric cancer cStage ⅣB treated with systemic chemotherapy at Yarita Hospital between January 2016 and December 2022. The following 2 groups were compared: early patients treated between 2016 and 2017 and late patients treated between 2018 and 2022. [Results]Nivolumab was used in 20 patients(30%), and there were no cases of discontinuation due to irAE. The median overall survival was 11 months(0-91 months), with a duration of 13 months in the early group and 8.5 months in the late group(p=0.02). The transition rate to the third-line or later treatments increased from 6 of 27 patients(22%)in the early group to 13 of 40 patients(33%)in the late group(p=0.02). [Discussion]For patients evaluated in this study, the first and second treatment courses were introduced in the short-term, with the hope of subsequent treatment, even for patients with large ascites, poor PS, or complications. In recent years, drugs for the fourth-line and later treatments have been introduced, and we have observed patients for whom the latter treatment was effective.[Conclusion]The transition rate to the third-line or later treatments of patients with unresectable gastric cancer is increasing.