Diagnostic accuracy and value of magnetic resonance imaging (MRI) in planning exenterative pelvic surgery for advanced colorectal cancer

Abstract

PurposeTo assess the diagnostic accuracy of magnetic resonance imaging (MRI) in detecting colorectal tumour invasion according to seven intrapelvic compartments for planning exenterative pelvic surgery. MethodSixty-three consecutive patients underwent preoperative MRI planning for exenterative surgery, defined as operative excision beyond conventional mesenteric planes for locally advanced (n=23) and recurrent (n=41) pelvic colorectal cancer. The institutional research committee approved of the study and waived the need for a consent form as the images were retrospectively assessed. Two radiologists reported tumour invasion for each of seven anatomic surgical resection compartments, blinded to histopathology and the intraoperative findings. Sensitivity, specificity and predictive values were calculated for the seven intrapelvic compartments. Cox regression analysis was used to calculate the risk of death and recurrence. Overall interobserver agreement was assessed using Cohen’s Kappa coefficient (k). ResultsThe sensitivity of MRI was ⩾93.3% in all but the lateral compartment where it was 89.3%. Specificity for the posterior (82.2%) and anterior compartments below the peritoneal reflection (86.4%) was lower compared to the other compartments. Agreement between the two radiologists was found to be good or very good for all compartments (k>0.72). An MRI diagnosis of tumour invasion in the anterior compartment above the peritoneal reflection was associated with a poorer survival (p=0.012). ConclusionMRI is accurate in predicting the extent of colorectal tumour within the pelvis and therefore can be used to determine the type of surgery required for curative resection. It should always be used to stage patients with advanced colorectal pelvic cancer.