IDO1 and neoplasm: In this study, we aimed to investigate whether the tumor IDO1 expression and CD8+TILs status would change after neoadjuvant therapy in ESCC, simultaneously compare the changes of tumor IDO1 expression and CD8+TILs status after NCRT and NCT, and evaluate the potential predictive role of the changes of tumor IDO1 expression and CD8+TILs status after neoadjuvant therapy on pathologic response and clinical outcome.