How could the TNM system be best adapted for staging rectal cancer in the future?

There exists a need for internationally standardized staging of tumors so that various factors, such as the stage at presentation, can be compared using epidemiological data from different countries and regions. The tumor, node, metastasis (TNM) staging system of the American Joint Committee on Cancer/International Union Against Cancer is now the standard for colorectal cancer staging. However, the rapid pace of medical advances has caused continued revision of pathologic staging in the TNM system. Numerous modifications have been made since its initial proposal, and many others are under investigation to address their role as prognostic and predictive indicators. This review focuses on the important changes from the fifth edition of the TNM staging system to the currently used seventh edition, and offer comments regarding possible future staging modifications that would appropriately accommodate the recent valuable findings.