Preoperative assessment of the circumferential margin in rectal cancer is more informative in treatment planning than the T stage.

Preventing local recurrence in rectal cancer means achieving a free circumferential resection margin (CRM) through an optimal combination of surgery, radiotherapy and chemotherapy. This requires a differentiation between primary resectable and locally advanced cancers. The T staging used, while being a powerful marker of prognosis, has two major downsides. First, accuracy of preoperative predictions of the T stage is unacceptably low. Second, a T3 tumor can be either primary resectable or locally advanced. A review of the literature was performed to establish the value of the CRM as the preferred preoperative staging classification, and to establish the feasibility of predicting the CRM using modern day, high-resolution imaging techniques. We advocate using the CRM as preoperative staging classification. Magnetic resonance imaging and multislice computed tomography offer an accurate pre-operative prediction of the CRM, and staging by means of predicted CRM offers the ideal combination of accuracy and clinical relevance.