Lesion-level response to immune checkpoint inhibitor in patients with advanced gastric cancer.

Abstract

311 Background: The efficacy of anti-PD-1 monotherapy has been reported to be heterogeneous in each metastatic location in non-small cell lung cancer. Therefore, we analyzed the response of target lesions in each organ and the association between pattern of progression and survival in patients with gastric cancer (GC). Methods: We performed retrospective analysis, which include 148 patients with GC who received nivolumab or pembrolizumab treatment between 2017 and 2021 at eight institutions in Japan. Response rate (RR), progression free survival (PFS), and overall survival (OS) were evaluated in total patients. The percent change of target lesions of each organs was measured by CT using RECIST, and their best percent changes were compared. In the GC patients with best response of progression disease (PD), the association between pattern of progression and survival was analyzed. Systemic progression was defined as PD in two or more lesions including target or non-target lesions, and non-systemic progression was defined as PD in only one lesion. Results: Among 148 patients, the RR, median PFS, and median OS were 11.6%, 1.6 months (95%CI, 1.4-1.9), and 4.4 months (95%CI, 3.6-6.6), respectively. A total of 293 lesions from 112 patients with target lesions were examined. The median best percent change of lymph node (n = 76), liver (n = 62), peritoneum (n = 19) and lung (n = 8) was +2.3%, +27%, +12%, +8.5%, respectively. Liver had significantly the lowest responses compared with lymph node and peritoneum (p < 0.0001 and p = 0.016). The median OS in non-systemic and systemic progression group was 5.6 months (95%CI, 3.6-8.8) and 3.3 months (95%CI, 1.9-3.6) and survival of patients with non-systemic progression showed significantly longer than that of systemic progression (p = 0.012). According to univariate and multivariate analysis, poor performance status (PS) (HR 1.73, 95%CI, 1.00-2.87) and systemic progression (HR 3.09, 95%CI, 1.95-4.82) were associated with OS in total patients. Additionally, liver metastasis (OR 2.99, 95%CI, 1.04-8.58) was identified as a baseline factor associated with systemic progression in the univariate and multivariate analysis. Conclusions: The efficacy of immune checkpoint inhibitor (ICI) is dependent on the metastatic location. Moreover, pattern of progression has been associated with overall survival. Liver metastasis might be a predictive factor of systemic progression in ICI treatment for GC.