Clinical benefit of continuation of PD-1 inhibitors after progression on first-line chemoimmunotherapy in metastatic gastric cancer and biomarker exploration

BackgroundWhether continuing immunotherapy after progression in second-line settings of metastatic gastric cancer (MGC) remains unclear. Herein, we explored the efficacy of PD-1 inhibitors for MGC after progression on previous chemoimmunotherapy.MethodsWe retrospectively identified MGC patients who received oxaliplatin-based chemotherapy plus PD-1 inhibitor, with or without trastuzumab, as first-line treatment. The patients received treatment with or without PD-1 inhibitors beyond progression in patients with MGC were divided into treatment beyond progression (TBP) group and non-TBP (NTBP) group. The median progression free survival (PFS) and overall survival (OS) from the start of treatment after progression were assessed.ResultsThe mOS and mPFS in the TBP group was significantly longer than that in the NTBP group (mOS: 9.0 vs. 5.0 months, P = 0.011; mPFS: 4.3 vs. 2.7 months, P = 0.03). Moreover, TBP was an independent prognostic factor for both PFS and OS in multivariate analysis. In the subgroup analysis, patients who were male, had a favorable ECOG (0-1), classified into diffuse histologic subtype and achieved disease control in the prior chemoimmunotherapy, might be more likely to benefit from continuing immunotherapy compared to discontinuation beyond progression.ConclusionPD-1 inhibitors based therapeutic strategy may be a reasonable option in second-line setting for MGC who progressed on prior immunotherapy. Further larger prospective trials are warranted to validate these findings.