The Clinical Impact of the Tumor Stroma Ratio in Gastrointestinal Cancer Treatment.

The standard treatment for gastrointestinal cancer is surgical resection and perioperative adjuvant treatment. Thus far, gastrointestinal cancer research has mainly focused on cancer cells themselves. Recently, the tumor microenvironment (TME) has been a subject of investigation. The TME is a complex system composed of various cell types, including tumor cells, endothelial cells, stromal cells, immune cells, and extracellular components. Among them, the stromal cells surrounding tumor cells are being investigated in gastrointestinal cancers. Stromal cells play a role in tumor growth, invasion, and metastasis. Moreover, stromal cells are associated with increased chemotherapy resistance and reduced chemotherapy delivery. Therefore, it is necessary to develop prognostic or predictive factors that consider the tumor-stroma interaction. The tumor stroma ratio (TSR) has recently been shown to be a promising outcome prediction tool in various malignancies. The TSR is based on the proportion of the stroma to tumor area. Recent studies demonstrated that a high amount of stroma or low TSR was associated with a poor prognosis and was a predictor of various treatment modalities. Therefore, to optimize the gastrointestinal cancer treatment, it is necessary to understand the role of the TSR in gastrointestinal cancers. This review summarizes the background, current status, and future perspectives of the TSR for gastrointestinal cancer treatment.