Prognostic Implications of Infiltrating T Cells Within Tumors for Patients With Esophageal Squamous Cell Carcinoma: A Retrospective Cohort Study

Background: Infiltrating T lymphocytes within tumors have been recognized to be associated with patient survival in various cancer types. For esophageal squamous cell carcinoma (ESCC), the prognostic implications of infiltrating CD3+ and CD8+ T cells have yet to be validated in more extensive patient groups.Methods: We evaluated the numbers of infiltrating CD3+ and CD8+ T cells within tumors from 461 patients with ESCC using immunohistochemistry and analyzed its impacts on overall survival.Results: The median number of infiltrating CD3+ and CD8+ T cell per field was 16.0 (P25-P75: 9.2-28.6) and 8.0 (3.8-20.2), respectively, with obvious correlation between them (rs = 0.65, p < 0.0001). Age and tumor grade were associated with the numbers of infiltrating T cells (all p < 0.05). A high number of infiltrating CD3+ T cells was associated with prolonged overall survival (unadjusted HR for high vs low: 0.73, 95% CI: 0.55-0.98), whereas CD8+ T cell number was not (0.90, 0.68-1.20). Multivariate Cox analysis identified that T stage, lymph node metastasis, and infiltrating CD3+ T cell number were independent prognostic factors (all p < 0.05).Conclusions: Our results indicate that CD3+ T cell infiltration within tumors is an independent prognostic factor for ESCC patients, whereas CD8+ T cell infiltration has no prognostic implications.