In addition, the subgroup analyses performed according to cancer types indicated that in nasopharyngeal carcinoma (HR: 2.01, 95% CI: 1.03–3.91), esophageal carcinoma (HR: 1.72, 95% CI: 1.23–2.42), glioblastoma (HR: 2.76, 95% CI: 1.49–5.14), and malignant hematologic diseases (HR: 1.43, 95% CI: 1.00–2.05), CTLA-4 was a good prognostic indicator, while CTLA-4 was associated with poor outcome in malignant pleural mesothelioma (HR: 0.54, 95% CI: 0.35–0.85). Here, CTLA4 is linked to malignant pleural mesothelioma.