Analysis of resection margins and prognostic risk factors for T1 colorectal cancers treated by endoscopic submucosal dissection

Aims Endoscopic submucosal dissection (ESD) is widely regarded as the preferred technique for removing large benign colorectal lesions and those at risk of submucosal invasive cancer (SMIC), with the aim of ensuring en-bloc resection. Achieving R0 resection is a critical factor to allow organ-preservation strategies, particularly in cases of endoscopic resection of T1-colorectal cancer (T1-CRC). We aim to evaluate the R0 resection rate with assessment of vertical and lateral margins, and the presence of prognostic risk factors, in a large cohort of colorectal ESDs. Furthermore, we aim to identify predictive factors associated with vertical margin involvement.

Methods Multicenter prospective cohort study in 13 centers (NCT04592003), including all colorectal ESDs between 09/2019 and 09/2024. Procedural and histological outcomes were analyzed using univariate and multivariate analysis.

Results 7495 large colorectal polyps were included, of which 781 were T1-CRCs with a median size of 45 mm [35-65]. En bloc resection occurred in 96.7% and R0 resection in 74.9%. Lateral resection margins were free in 92.5%, with positive margins for adenocarcinoma in only 0.8% (low grade dysplasia in 2.6%, high grade in 1.2%, missing data in 2.6%). Vertical margins were free in 80.3%, and decreased significantly when deep SMIC was present to 75.0%, compared to 95.7% for superficial SMIC. However deep SMIC with up to 2000 µm invasion depth, demonstrated free vertical resection margins in still 80.7%, after which it gradually decreased to 73.1% and 67.7% at an infiltration depth of 2000-3000 µm and>3000 µm respectively. Predictive factors for free vertical resection margins include lesion size>50mm (OR=1.66, [1.01;2.71], p=0.045) and rectal localization (OR=1.86, [1.04;3.3], p=0.035). Significant difference was observed in the presence of prognostic risk factors between superficial and deep SMIC, with lympho-vascular invasion (LVI) in 9.6%, and high-grade tumor budding (Bd) in 17.1% for superficial SMIC, compared to 25.0% and 30.0% respectively, in deep SMIC. However, absence of LVI, Bd or poor differentiation was noted in 75.9% of superficial and 61.7% of deep T1-CRC. Concerning deep SMIC, no relation was observed in the presence of these risk factors with respect to the depth of infiltration.

Conclusions After ESD for T1-CRC, the likelihood of achieving free vertical resection margins decreases significantly when the invasion depth exceeds 2000µm. Therefore, careful selection of lesions using optical diagnosis is essential. For T1-CRC with deeper invasion, consideration should be given to intermuscular dissection to enchance the chances of organ preservation. Striving for R0 resection remains crucial, as additional prognostic factors are present in approximately 38% of cases, regardless of the invasion depth of SMIC.

Publication History

Article published online:
27 March 2025