CTLA4 and esophageal squamous cell carcinoma: Univariate analysis (log-rank) revealed that mean OS was longer in Group 4 (62.705 months, Table 3; P = 0.009, Table 4) than in Group 1 (43.822 months, Table 3; P = 0.005, Table 4), Group 2 (45.702 months, Table 3; P = 0.001, Table 4) and Group 3 (49.712 months; Table 3; P = 0.007, Table 4), indicating that higher intratumoral CTLA-4 expression was associated with increased risk of death from ESCC (Figure 2C).