Comparison of response evaluation criteria in solid tumors and tumor regression grade in evaluating the effect of preoperative systematic therapy of gastric cancer.

Abstract

e16063 Background: Both Response Evaluation Criteria in Solid Tumors (RECIST) and tumor regression grade (TRG) play key roles in evaluating tumor response. However, the consistency of these two methods has not been determined. Therefore, we compared the prognostic value of TRG and RECIST 1.1 for gastric cancer (GC) patients and analyzed their consistency. Methods: Patients with gastric cancer who received preoperative chemotherapy or chemotherapy combined with immunotherapy and had record of TRG from December 2013 to October 2021 were enrolled retrospectively. TRG 0-1 is considered as consistent with CR or PR in RECIST 1.1 and TRG 2-3 corresponds to SD or PD in RECIST 1.1. The primary endpoints were disease free survival (DFS) and overall survival (OS). The consistency of RECIST and TRG was examined by kappa statistics. Kaplan-Meier method and Cox proportional hazards regression models were used for survival analysis. Results: We enrolled 157 GC patients, including 125 patients with preoperative chemotherapy, and 32 patients with preoperative chemotherapy combined with PD-1 inhibitors. Among them, 56 patients had measurable lesions. Only 19.6% (11/56) of the patients had consistent results of RECIST 1.1 and TRG. The pCR rate was 13.4% and the overall response rate (ORR) was 52.6% according to RECIST 1.1. Preoperative chemoimmunotherapy had a significantly higher pCR rate than chemotherapy alone, 34.4% vs 8.0%, P< 0.001. TRG was significantly correlated with both OS and DFS (P = 0.0162 and 0.0259, respectively) while response according to RECIST1.1 was not significantly related with OS and DFS ( P= 0.8598 and 0.2288, respectively). The median DFS had not reached in the TRG 0-1 group and was 16.13 months in TRG 2-3 group. Young patient, peritoneal metastasis or liver metastasis was correlated with TRG 2-3. Conclusions: Our results showed that TRG was in poor agreement with RECIST 1.1. TRG was better than RECIST 1.1 in predicting DFS and OS for GC patients who received neoadjuvant therapy.