Residual Tumor Characteristics of Esophageal Squamous Cell Carcinoma after Neoadjuvant Chemoradiotherapy

Abstract Objective To investigate the characteristics of residual tumors of esophageal squamous cell carcinoma (ESCC) after neoadjuvant chemoradiotherapy (nCRT). Methods The resection specimens of 187 patients undergoing surgery after nCRT in Zhongshan Hospital of Fudan University were re-evaluated. Tumor regression grade (TRG) determined by residual tumors ratios was scored for each specific layer of the esophageal wall and all removed lymph nodes for 4 grades as TRG1, 0% residual tumors, TRG2, 50%. The prepT and prepN parameters were recorded reflecting the original depth of primary tumor and number of originally involved lymph nodes, respectively. According to regression directionality, regression pattern was classified into 4 categories as Type I: regression towards the lumen, Type II: regression towards the invasive front, Type III: concentric regression, and Type IV: scattered regression. Statistical analyses were performed using Mann-Whitney, Chi-square, Cochran Q tests, and Kendall τ-b coefficient, appropriately. Results 138 patients have residual tumors, and 97 (70.3%), 100 (72.5%), 89 (64.5%), 63 (45.7%) and 68 (49.3%) patients have malignant cells in mucosa, submucosa, muscularis propria, adventitia/surrounding stroma and lymph nodes, respectively. A total of 115 (83.3%) patients had residual tumors in the mucosa or submucosa, but 63 (54.8%) were graded as TRG2 with small amounts of tumors in these two layers, 9 (6.5%) patients had residual tumors in the deep two layers, and 14 (10.1%) only in lymph nodes. Overall, 86 (62.7%) patients with residual tumors are difficult to identify via present techniques. In prepT3-4 patients, only muscularis propria contained residual tumors significantly more frequently than the adventitia/surrounding stroma (P Conclusions The small amount of viable tumor cells in the superficial layers, low pCR rate of lymph nodes, and diverse regression patterns lead to difficulty of detecting residual tumors in ESCC.