Tumor regression grade (TRG) for gastric cancer and radiological methods on predicting response to perioperative chemotherapy: a narrative review

Background and Objective: Perioperative chemotherapy has been increasingly practiced on gastric cancer (GC) in Western Countries where two third of the patients have locally advanced disease at diagnosis. The histological and radiological evaluation of the tumor response to chemotherapy are both cornerstones of this multimodal therapy to predict the oncological outcomes. This article aims to review the current tumor regression grade (TRG) classification systems available and give an overview regarding radiological methods on predicting response to therapy.