An ancillary analysis of the Japanese Phase III trial JCOG1013 suggests that tumor PD-L1 expression, measured as a tumor proportion score (TPS), is associated with improved survival in unresectable or recurrent gastric cancer patients treated with first-line chemotherapy alone. The analysis reports TPS at or above 1% as an independent favorable prognostic factor. The study focused on patients not receiving immune checkpoint inhibitors, separating prognostic value from treatment benefit in an immunochemotherapy setting. If validated, PD-L1 could serve as a prognostic stratification factor for chemotherapy-only protocols. Clinically, the key question will be whether PD-L1 TPS can refine risk grouping in non-immunotherapy regimens without being conflated with the predictive effects of checkpoint blockade.