MRI after treatment of locally advanced rectal cancer: how to report tumor response--the MERCURY experience.

The Magnetic Resonance Imaging and Rectal Cancer European Equivalence (MERCURY) Study validated the use of MRI for posttreatment staging and its correlation with survival outcomes. As a consequence, reassessment of MRI scans after preoperative therapy has implications for surgical planning, the timing of surgery, sphincter preservation, deferral of surgery for good responders, and development of further preoperative treatments for radiologically identified poor responders. In this article we report a validated systematic approach to the interpretation of MR images of patients with rectal cancer after chemoradiation.