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

Abstract

370 Background: Exenterative pelvic surgery is challenging and has been used in colorectal surgery to manage patients with advanced colorectal pelvic cancer. Resection of the tumor needs to be performed en-bloc and if feasible, without exposing the tumor, since this can compromise resection margins. This can only be performed through careful pre-operative staging. This study aimed to assess the diagnostic accuracy of MRI in detecting colorectal tumor invasion into seven intrapelvic compartments and its value in planning exenterative pelvic surgery. Methods: Sixty four consecutive patients underwent preoperative MRI planning for exenterative surgery, for locally advanced (n= 23) and recurrent (n= 41) pelvic colorectal cancer. Two radiologists reported tumor invasion for each of the seven anatomic surgical resection compartments and were blinded to histopathology and intraoperative reference standards. Sensitivity, specificity and predictive values were calculated for each compartments. Kaplan-Meier methodology was used to calculate survival rates. Interobserver agreement was assessed using Cohen's Kappa coefficient (k). Results: The sensitivity of MRI was ≥93.3% in all except for the lateral compartment where it was 89.3%. Its specificity for the posterior (82.2%), anterior below (86.4%) the peritoneal reflection compartments was lower compared to the rest of the compartments. MRI diagnosis of lateral (OR= 11.41, p= 0.033), anterior compartment above the peritoneal reflection (OR= 3.14, p= 0.005) and multicompartmental involvement (OR= 1.99, p<0.001) was associated with higher risk of incomplete resection which was subsequently found to be significant factor in predicting overall and disease free survival (p<0.05). The agreement between the two radiologists was found to be either good or very good for all the compartments (k>0.72). Conclusions: MRI is highly accurate in predicting tumor invasion within the intrapelvic compartments and it should be the pre-operative staging modality of choice when considering exenterative surgery for patients with locally advanced colorectal pelvic cancer. [Table: see text]