Magnetic resonance imaging based rectal cancer classification: landmarks and technical standardization

Area of Science:

• Oncology
• Radiology
• Surgical Oncology

Background:

• Accurate rectal cancer classification is crucial for determining preoperative chemoradiation therapy and selecting surgical techniques.
• Existing Western and Japanese classifications have limitations in guiding precise management.
• Magnetic Resonance Imaging (MRI) offers detailed anatomical visualization for improved classification.

Purpose of the Study:

• To propose and validate a novel MRI-based classification system for rectal cancer.
• To correlate tumor location and invasion with specific anatomical landmarks on MRI.
• To standardize surgical and chemoradiation management based on the new classification levels.

Main Methods:

• A retrospective review of 60 rectal cancer patients was conducted.
• A new classification system was developed based on tumor distal margin relative to the peritoneal reflection and levator ani muscle on MRI.
• The proposed classification was compared with existing Western and Japanese classifications.

Main Results:

• The new MRI classification divided rectal cancers into four distinct levels, correlating with specific surgical approaches and chemoradiation use.
• Level I (above peritoneal reflection) predominantly received low anterior resection (LAR) without chemoradiation.
• Level IV (below levator ani insertion) showed a high rate of abdominoperineal resection (APR) with chemoradiation; an overall kappa of 0.93 indicated near-perfect agreement between surgeons and radiologists.

Conclusions:

• The proposed MRI-based rectal cancer classification facilitates prediction of surgical and chemoradiation management.
• This classification enhances communication within multidisciplinary teams.
• The system demonstrates high inter-observer reliability, suggesting its clinical utility.