International study group on rectal cancer regression grading: interobserver variability with commonly used...

Area of Science:

• Gastroenterology
• Oncology
• Pathology

Background:

• Rectal cancer treatment often involves neoadjuvant chemoradiation.
• Accurate assessment of treatment response, specifically tumor regression, is crucial for patient management.
• Current regression grading systems lack standardization and reproducibility.

Purpose of the Study:

• To evaluate the inter-observer concordance among gastrointestinal pathologists for rectal cancer regression grading.
• To assess the performance of Mandard, Dworak, and a modified rectal cancer regression grading systems.
• To identify the need for improved regression grading methodologies.

Main Methods:

• Seventeen gastrointestinal pathologists assessed 10 digitized rectal cancer slides from patients treated with neoadjuvant chemoradiation.
• Pathologists utilized the Mandard, Dworak, and a modified rectal cancer regression grading systems.
• Inter-observer concordance was quantified using Kappa (κ) values.

Main Results:

• Very low concordance was observed across all three grading systems (κ values: 0.28-0.38).
• Unanimous agreement was achieved in only one case using the modified system.
• The study highlighted a lack of precision and clarity in existing grading systems.

Conclusions:

• Current regression grading systems for neoadjuvant chemoradiation-treated rectal cancer exhibit poor inter-observer reliability.
• There is a significant need for a simplified, reproducible grading system with clear criteria.
• A composite scoring approach and standardized specimen sampling are recommended for improved accuracy.