Abstract
BACKGROUND: While the benefit of immune checkpoint inhibitors (ICI) is well established in programmed death-ligand 1 high (PD-L1(high)) advanced gastroesophageal adenocarcinoma (GEAC), there remains significant controversy about their benefit in PD-L1(low) GEAC. To elucidate the benefit of ICI in PD-L1(low) and PD-L1(negative) GEAC, we conducted an analysis leveraging individual patient data (IPD) extracted from Kaplan-Meier (KM) plots of pivotal trials. METHODS: KM curves from randomized clinical trials investigating the efficacy of ICI for advanced GEAC were extracted from published articles. IPD were extracted from the reported curves, and, in the case of unreported KM plots, KMSubtraction was used to retrieve survival data. A patient-level meta-analysis was conducted for PD-L1(low) tumors. RESULTS: In the human epidermal growth factor receptor 2 (HER2)-negative setting, pooled PD-L1 combined positive score (CPS) 1-4 subgroup KM plots from KEYNOTE-859, CHECKMATE-649, and RATIONALE-305 showed a modest overall survival (OS) benefit with the addition of an anti-programmed cell death protein 1 (anti-PD-1) agent [hazard ratio (HR) 0.868, P = 0.018]. Similarly, a modest OS benefit was shown by our IPD meta-analysis of PD-L1 CPS 1-9 subgroups from KEYNOTE-859, KEYNOTE-062, and RATIONALE-305 (HR 0.840, P = 0.002.) Conversely, when CPS 5-9 subgroup KM plots from KEYNOTE-859 and RATIONALE-305 were pooled together, no significant OS benefit was found in the ICI-chemotherapy arm (HR 0.867, P = 0.181), although this subgroup was relatively small. CONCLUSIONS: In PD-L1(low) HER-2 negative GEAC, the benefit of first-line ICI is modest, yet significant. Further translational work is warranted to better select patients who could benefit from immunotherapy in this setting. Meanwhile, alternative therapeutic options such as zolbetuximab in Claudin18.2-positive disease must be taken into account.