Toward precision selection in endoscopic intermuscular dissection for rectal cancer

We read with great interest the article by van der Schee et al. on magnetic-resonance imaging (MRI)-based identification of rectal cancers amenable to endoscopic intermuscular dissection (EID) [1]. Their work marks a paradigm shift from conventional diagnostics focused on T1a/b distinction to one aimed at identifying T2_circ (invasion limited to the circular layer of the muscularis propria) versus T2_long (invasion extending into the longitudinal muscle layer). We applaud this diagnostic reorientation and would like to raise two points for further discussion.

First, the proposed 1-mm cutoff for preserved muscularis propria warrants scrutiny. Rectal wall thickness may vary based on rectal distension, patient age, presence of inflammatory bowel disease, and tumor location (upper, middle, or lower rectum) [2]. The 1-mm threshold is based on the assumption that the T2_long layer typically exceeds this depth. Histological data on the average muscularis propria thickness, especially T2_long, stratified by tumor location would help validate this assumption and improve confidence in the diagnostic criteria.

Second, the reported specificity of approximately 70% indicates a notable risk of understaging, with about 30% of more advanced cancers potentially being misclassified as eligible for EID. A more detailed review of these discordant cases would be valuable. Identifying common imaging artifacts, tumor features, or technical pitfalls may refine the interpretation of MRI findings. Additionally, combining MRI with endoscopic ultrasound may enhance depth of invasion accuracy [3].

Notwithstanding these considerations, we commend the authors for proposing a bold and structured framework that advances rectal-preserving strategies. As the population ages and the number of patients unfit for surgery increases, endoscopic resection of T2_circ tumors – those with lower risk of nodal metastasis – may become an increasingly important treatment option [4] [5]. We look forward to further validation of this approach and believe it represents a promising direction for individualized, less invasive care in colorectal oncology.

Publication History

Article published online:
24 September 2025

• References

• 1 van der Schee L, Carten R, Albers SC. et al. Assessing the accuracy of magnetic resonance imaging in identifying early rectal cancers suitable for endoscopic intermuscular dissection. Endoscopy 2025; 57
• 2 Santiago I, Figueiredo N, Pares O. et al. MRI of rectal cancer-relevant anatomy and staging key points. Insights Imaging 2020; 11: 100
• 3 Ichimasa K, Kudo SE, Hayashi T. et al. Potential indications for peranal endoscopic myectomy in lower rectal cancer. Gastrointest Endosc 2025; 101: 1244-1247
• 4 Ichimasa K, Foppa C, Kudo SE. et al. Artificial intelligence to predict the risk of lymph node metastasis in T2 colorectal cancer. Ann Surg 2024; 280: 850-857
• 5 Goglia M, Pavone M, D’Andrea V. et al. Minimally invasive rectal surgery: current status and future perspectives in the era of digital surgery. J Clin Med 2025; 14: 1234