CD274 and signet ring cell carcinoma: In univariate analysis of OS, second-line treatment (chemotherapy vs. immunotherapy rechallenge), PD-L1 expression (CPS < 1 vs. CPS ≥ 1), and pathological type (adenocarcinoma vs. signet ring cell carcinoma) were significantly associated with OS (p < 0.05), while other variables were not (p > 0.05).