Interobserver and Intraobserver Agreement for the Laterally Spreading Tumor Classification in Large (>2 cm)...

Area of Science:

• Gastroenterology
• Endoscopic Imaging
• Oncology

Background:

• Accurate morphological assessment of large colorectal laterally spreading tumors (LSTs) is crucial for predicting invasion risk and guiding resection.
• The widely used LST classification's diagnostic reliability has not been formally evaluated.

Purpose of the Study:

• To evaluate the diagnostic reliability and inter-observer agreement of the LST classification system among expert endoscopists.
• To assess factors influencing agreement, including lesion size, endoscopist characteristics, and classification simplicity.

Main Methods:

• A prospective, multicenter video-based study involving 24 blinded expert endoscopists.
• Independent classification of 46 LSTs twice, using a 5-subtype LST classification and a simplified 3-category model.
• Inter- and intra-observer agreement calculated using Light's kappa, with secondary analyses by lesion size, sex, and region.

Main Results:

• Poor inter-observer agreement was observed for the detailed LST classification (κ=0.37-0.36).
• Agreement varied geographically, with moderate agreement in Europe/Oceania and fair in North America/Asia.
• Simplifying to a 3-category model improved agreement to moderate (κ≈0.48); intra-observer agreement varied widely (κ=0.28-0.94).

Conclusions:

• Significant inter- and intra-observer variability exists for the LST classification among international experts.
• Current detailed LST subclassification shows low diagnostic reliability, necessitating improved standardization.
• Caution is advised when using detailed LST subclassification for clinical decisions or research endpoints.