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[The optimult study concept - selective neoadjuvant chemoradiation therapy based on preoperative MRI].

Optimal surgery for rectal cancer, i. e., total mesorectal excision in the middle and lower rectum reduces local recurrence substantially. Multi-modal therapy further improves the rate of local recurrence in advanced rectal cancer. In Germany neoadjuvant chemoradiation therapy is most frequently given for these tumours. However, clinical staging by endosonography, CT scan and / or MRI is unreliable, particulary as regards lymph node category, which entails overtreatment of a relevant number of patients secondary to overstaging. Thus, a subgroup of patients has to tolerate side effects and long-term sequelae of neoadjuvant therapy without having oncological benefit from this pretreatment. It is of note that the prognosis of patients with advanced rectal cancer depends not only on the T and N category but also on the free circumferential margin of the tumour as determined by pathological examination. In contrast to the T and N category, the latter may be predicted before treatment by pelvic MRI. While several case series demonstrated that low local recurrence rates are achieved in patients when preoperative MRI showed free circumferential margins, this concept was never tested in a randomised controlled trial. We, therefore, designed a two-armed randomised study with patients who suffer from rectal cancer and who have 2 mm or more free circumferential margins on their preoperative MRI. These patients are either operated without pretreatment (intervention arm) or receive neoadjuvant chemoradiation therapy with subsequent surgery (control arm). If local recurrence in the intervention arm is not inferior to the control arm, this study may form the basis for an individualised therapeutic concept for rectal cancer based on preoperative MRI. Potentially, chemoradiation therapy may be avoided in the future for patients who will have no oncological benefit from this treatment modality.