Inter and intra-observer agreement for the LST Classification in Large (>2cm) Colorectal Laterally Spreading Tumours

BACKGROUND: Morphological assessment of large (≥20 mm) colorectal laterally spreading tumors (LSTs) is central to predicting submucosal invasion risk, procedural difficulty, and optimal resection strategy. The LST classification is widely used; however, its diagnostic reliability has never been formally evaluated. PATIENTS AND METHODS: We performed a prospective multicenter video-based study. 24 blinded expert endoscopists from North America, Europe, Asia, and Oceania independently classified video recorded LSTs twice, in randomized order, into 5 prespecified LST subtypes. Inter- and intra-observer agreement were calculated using Light's kappa. Secondary analyses evaluated agreement by LST size category, endoscopist sex, geographic training region, and a simplified 3-category granular vs non-granular classification. RESULTS: 46 LSTs were evaluated, yielding 1104 classifications. Inter-observer agreement for the primary outcome was poor in both the first (κ=0.37) and second assessment rounds (κ=0.36). Agreement varied modestly across LST size groups and endoscopist characteristics, with moderate agreement in Europe and Oceania and fair agreement in North America and Asia. Simplifying morphology into 3 categories improved inter-observer agreement to the moderate range (κ≈0.48). Intra-observer agreement ranged widely (κ=0.28-0.94), with the highest reproducibility among endoscopists trained in Europe and Oceania. Intra-observer agreement was generally higher for smaller lesions (<40 mm) and improved when using the 3-category model. CONCLUSIONS: Among international experts, inter-observer agreement for the LST classification is low, with considerable inter- and intra-observer variability. These findings highlight the need for improved standardization and suggest caution when using detailed LST subclassification for clinical decision-making or as an endpoint in research.

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Journal
The American Journal of Gastroenterology
Published
2026-06-30
DOI
https://doi.org/10.14309/ajg.0000000000004103
Primary Topic
Gastric Cancer Management and Outcomes
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article
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article

Inter and intra-observer agreement for the LST Classification in Large (>2cm) Colorectal Laterally Spreading Tumours

Mathieu Pioche, Heiko Pohl, Lucile Héroin, Roupen Djinbachian et al.
The American Journal of Gastroenterology
Gastric Cancer Management and Outcomes
article

Inter and intra-observer agreement for the LST Classification in Large (>2cm) Colorectal Laterally Spreading Tumours

Mathieu Pioche, Heiko Pohl, Lucile Héroin, Roupen Djinbachian, Yusuke Fujiyoshi, Nima Mottacki, Yutaka Saito, Isabelle Lienhart-Chambon, Robert Bechara, Philippe Leclercq, Amrita Sethi, Jeffrey D. Mosko, Sandro Sferrazza, Victoire Michal, Nicholas G. Burgess, Jérémie Jacques, Ludovico Alfarone, Douglas K. Rex, Charles Ménard, Enrique Rodríguez de Santiago, Mariana Figueiredo, Michal F. Kaminski, Neal Shahidi, A Lupu, Dennis Yang, Daniel von Renteln, Eric Lam
article en

Abstract

BACKGROUND: Morphological assessment of large (≥20 mm) colorectal laterally spreading tumors (LSTs) is central to predicting submucosal invasion risk, procedural difficulty, and optimal resection strategy. The LST classification is widely used; however, its diagnostic reliability has never been formally evaluated. PATIENTS AND METHODS: We performed a prospective multicenter video-based study. 24 blinded expert endoscopists from North America, Europe, Asia, and Oceania independently classified video recorded LSTs twice, in randomized order, into 5 prespecified LST subtypes. Inter- and intra-observer agreement were calculated using Light's kappa. Secondary analyses evaluated agreement by LST size category, endoscopist sex, geographic training region, and a simplified 3-category granular vs non-granular classification. RESULTS: 46 LSTs were evaluated, yielding 1104 classifications. Inter-observer agreement for the primary outcome was poor in both the first (κ=0.37) and second assessment rounds (κ=0.36). Agreement varied modestly across LST size groups and endoscopist characteristics, with moderate agreement in Europe and Oceania and fair agreement in North America and Asia. Simplifying morphology into 3 categories improved inter-observer agreement to the moderate range (κ≈0.48). Intra-observer agreement ranged widely (κ=0.28-0.94), with the highest reproducibility among endoscopists trained in Europe and Oceania. Intra-observer agreement was generally higher for smaller lesions (<40 mm) and improved when using the 3-category model. CONCLUSIONS: Among international experts, inter-observer agreement for the LST classification is low, with considerable inter- and intra-observer variability. These findings highlight the need for improved standardization and suggest caution when using detailed LST subclassification for clinical decision-making or as an endpoint in research.

The American Journal of Gastroenterology
St. Michael's Hospital (CA), Université de Sherbrooke (CA), University of British Columbia (CA), University of Ottawa (CA), University of Toronto (CA), Columbia University Irving Medical Center (US), AdventHealth Orlando (US), Ottawa Hospital (CA), Westmead Hospital (AU), White River Junction VA Medical Center (US), Centre Hospitalier Universitaire de Limoges (FR), National Institute of Oncology (HU), Hôpital Edouard Herriot (FR), Instituto Ramón y Cajal de Investigación Sanitaria (ES), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (ES), Centre Hospitalier Annecy Genevois (FR), National Cancer Center Hospital East (JP), Azienda di Rilievo Nazionale ed Alta Specializzazione (IT), Centre Hospitalier Universitaire de Saint-Pierre (BE), Kingston Health Sciences Centre (CA), IRCCS Humanitas Research Hospital (IT), Hôpital Civil, Strasbourg (FR), Ottawa Hospital Research Institute (CA), Indiana University School of Medicine, Indiana University – Purdue University Indianapolis (US), University of Gothenburg (SE), KU Leuven (BE)
Openalex Percentile: Top 8%
Gastric Cancer Management and Outcomes
DOISourceOpenAlex
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