Risk factors for residual cancer and lymph node metastasis after non-curative endoscopic resection of colorectal...

Following a non-curative endoscopic resection of T1 colorectal cancer, current guidelines recommend additional surgery based on high-risk pathological features. However, the actual rates of residual disease, such as residual cancer and lymph node metastasis (LNM), remain unclear and risk factors vary significantly across studies. We aimed to determine the true incidence of residual cancer and LNM and identify independent risk factors to guide surgical decision-making.

This multicenter retrospective study included patients who underwent radical surgery after non-curative endoscopic resection of T1 colorectal cancer at four hospitals between 2015 and 2020. Non-curative resection was defined by positive margins, deep submucosal invasion (≥ 1000 μm), poor differentiation, lymphovascular invasion, or high-grade tumor budding in accordance with current guidelines.

Among 517 patients, residual cancer was found in 3.7% and LNM in 7.7% of the cases. Independent predictors of residual cancer were ESD procedure (OR 9.87, P < 0.001), piecemeal resection (OR 5.51, P = 0.017), positive lateral margin (OR 5.88, P = 0.004), and positive deep margin (OR 10.30, P = 0.003). For LNM, submucosal invasion depth ≥ 1000 μm (OR 4.66, P = 0.015), poor differentiation (OR 4.30, P = 0.026), lymphovascular invasion (OR 2.42, P = 0.016), and positive deep margin (OR 2.26, P = 0.018) were significant risk factors. Risk increased substantially with cumulative factors: patients with 0-1 risk factors had minimal residual cancer rates (< 1%), while those with ≥ 2 factors showed exponentially higher risks.

The actual incidence of residual cancer and LNM after non-curative endoscopic resection is relatively low. A stepwise framework that evaluates local completeness and LNM risk independently and then integrates the two assessments may support individualized decision-making, potentially sparing low-risk patients from radical surgery while ensuring appropriate intervention for high-risk patients.