Local staging of anal and distal colorectal tumors with the magnetic resonance endoscope

Background: We prospectively assessed the feasibility and accuracy of endoscopic magnetic resonance (EMR) scanning in the local staging of anal and colorectal cancer as compared to endosonography. Methods: Fifteen patients with biopsy-proven anal (n = 2), rectal (n = 11), and distal colonic (n = 2) cancer underwent endosonography followed by EMR imaging. Scans were acquired using the magnetic resonance receiver coil incorporated into the tip of the non-ferromagnetic endoscope. Blinded to endosonography results, two radiologists interpreted the EMR images using the TNM system. Staging results were compared to endosonography in all patients and to histopathology in the 13 colorectal cases. Results: EMR imaging, well tolerated in all patients, correlated with endosonography in 10 of 15 and 12 of 15 cases for T- and N-staging, respectively. In the 13 colorectal patients with available histopathology, accuracy of EMR and of endosonography in T-staging was 77% and 85%, respectively; N-staging accuracy was 62% for both. Conclusions: For anal and distal colorectal neoplasms, EMR imaging is feasible and provides local staging comparable to endosonography.