Background: Recently, several immune checkpoint inhibitors have been developed and are being used to treat malignant melanoma, lung cancer, and other cancers. Several reports have indicated that tumor-infiltrating lymphocytes (TILs) are associated with clinical and histopathologic risk factors in various cancers. However, the role of TILs in esophageal squamous cell carcinoma (ESCC) has not been well studied. This study aimed to investigate the perilesional status of TILs in ESCC and to show associations between TILs and clinical variables. Methods: The study enrolled 277 ESCC patients. Evaluation of TILs was performed according to the criteria of the International TILs Working Group 2014, and associations between TIL and clinicopathologic variables were examined. Results: Most of the clinicopathologic factors were not statistically associated with TIL status. The number of patients who received adjuvant therapy was significantly larger in the TIL-negative group. Cancer-specific survival (CSS) of patients in the TIL-positive group was significantly better than in the TIL-negative group. Among the patients who received adjuvant therapy, CSS was significantly better in the TIL-positive group than in the TIL-negative group. Uni- and multivariate analyses identified tumor depth and TIL status as independent prognostic factors for CSS. Among the other clinicopathologic variables, TIL status was the strongest CSS indicator. Conclusion: Tumor-infiltrating lymphocyte status is a strong predictor of good prognosis for ESCC patients.
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