Tumor Remission and Tumor-Infiltrating Lymphocytes During Chemoradiation Therapy: Predictive and Prognostic Markers in Locally Advanced Esophageal Squamous Cell Carcinoma

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Clinical tools are unavailable for accurate prediction of pathologic responses to chemoradiation therapy (CRT) among patients with esophageal squamous cell carcinoma (ESCC) before surgery. We evaluated tumor remission and tumor-infiltrating lymphocytes (TILs) during CRT as predictors of pathologic response and prognostic markers for patients with locally advanced ESCC treated with neoadjuvant CRT (neo-CRT) or definitive CRT. We analyzed patients with locally advanced ESCC (N = 164) who underwent neo-CRT (N = 48) or definitive CRT (N = 116). Patients underwent endoscopic ultrasonography and biopsies when induction CRT finished. Tumor remission characteristics were designated minor (-/+) to excellent remission (ER) (+++). TILs were determined in 10% increments. Tumor remission, TILs, or both were associated with pathologic complete response (pCR) and survival in the neo-CRT group and then analyzed in the definitive CRT group. ER and lymphocyte-predominant ESCC (LPE; ≥60% TILs) were identified according to the pCR rate and disease-free survival. We built a prediction model for pCR incorporating ER and LPE. The area under the receiver operating characteristic curve was 0.877, and sensitivity and specificity were 86.7% and 90.9%, respectively. Furthermore, this model identified pathologic response with an excellent calibration. Disease-free survival of patients with ER and LPE tumors was significantly longer than that of other patients. When we included tumor remission and TILs during CRT, our model predicted pCR with high probability and helped stratify prognostic subgroups, thereby guiding future therapy decisions for patients with locally advanced ESCC. Validation of this model in larger, prospective, multicenter studies is essential.