Staging rectal cancer: MRI compared to MDCT.

Area of Science:

• Radiology
• Oncology
• Surgical Pathology

Background:

• Accurate assessment of the circumferential resection margin (CRM) is crucial for rectal cancer staging and treatment planning.
• Pre-operative imaging aims to predict tumor proximity to the CRM, guiding surgical strategy and prognosis.

Purpose of the Study:

• To audit the accuracy of pre-operative Magnetic Resonance Imaging (MRI) and multi-detector row Computed Tomography (CT) in determining the relationship between rectal tumors and the CRM.
• To compare the imaging-based assessment of CRM involvement with post-operative histopathology findings.

Main Methods:

• Retrospective review of MRI and CT scans from 72 patients with rectal adenocarcinoma.
• Two independent observers classified tumor proximity to the mesorectal fascia into three categories: uninvolved, threatened, or involved.
• Agreement with post-operative histopathology was statistically assessed using Kappa analysis.

Main Results:

• Both MRI and CT demonstrated poor agreement with post-operative histology in predicting CRM status.
• A tendency for both modalities to overstage patients with an uninvolved CRM was observed.
• However, high negative predictive values were reported: 81.8% for MRI and 84.6% for CT for an uninvolved margin.
• No cases with histopathologically involved margins were missed by either imaging technique.

Conclusions:

• Pre-operative MRI and multi-detector row CT possess high negative predictive values for identifying an uninvolved rectal resection margin.
• These imaging modalities are valuable in ruling out CRM involvement, supporting surgical decision-making in rectal cancer management.