Baseline lesion number as an efficacy predictive and independent prognostic factor and its joint utility with TMB for PD-1 inhibitor treatment in advanced gastric cancer

Abstract

Background: We previously reported tumor mutation burden (TMB) as a potential prognostic factor for patients with advanced gastric cancer (AGC) receiving immunotherapy. We aimed to comprehensively understand the impact of tumor burden and TMB on efficacy and prognosis in immunotherapy-treated AGC patients. Methods: A total of 58 patients with refractory AGC receiving PD-1 inhibitor monotherapy from a phase Ib/II clinical trial (ClinicalTrials.gov identifier: NCT02915432) were retrospectively included. Univariate and multivariate logistical regression analyses and the Cox proportional hazards model were performed for prognostic value of baseline factors. Factors reflecting baseline tumor burden, including baseline lesion number (BLN), the maximum tumor size (MTS) and the sum of target lesion size (SLS) were analyzed. The objective response rate (ORR) and disease control rate (DCR) were compared by Chi-square test. Results: In univariate analysis, high BLN was associated with poor median progression-free survival (mPFS) [1.7 months versus 3.4 months; hazard ratio (HR), 2.696, p 0.05; 86.96% versus 54.29%, p < 0.05). When combining BLN and TMB, the best efficacy and survival were observed in the BLN low TMB high group (ORR: 37.5%, DCR: 62.5%, mPFS and mOS: not reached). The worst efficacy and survival were shown in the BNL high TMB low group [ORR: 0% (0/15); DCR: 13.3%; mPFS: 1.7 months; mOS: 2.7 months (all p < 0.05)]. Conclusions: BLN, rather than factors regarding baseline tumor size, is perhaps a potential predictor for benefit from immunotherapy and its combination with TMB could further risk-stratify patients with AGC receiving immunotherapy.