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ObjectiveIt is difficult to predict the presence of histological risk factors for lymph node metastasis (LNM) before endoscopic treatment of T1 colorectal cancer (CRC). Therefore, endoscopic therapy is propagated to obtain adequate histological staging. We examined whether secondary surgery following endoscopic resection of high-risk T1 CRC does not have a negative effect on patients' outcomes compared with primary surgery.DesignPatients with T1 CRC with one or more histological risk factors for LNM (high risk) and treated with primary or secondary surgery between 2000 and 2014 in 13 hospitals were identified in the Netherlands Cancer Registry. Additional data were collected from hospital records, endoscopy, radiology and pathology reports. A propensity score analysis was performed using inverse probability weighting (IPW) to correct for confounding by indication.Results602 patients were eligible for analysis (263 primary; 339 secondary surgery). Overall, 34 recurrences were observed (5.6%). After adjusting with IPW, no differences were observed between primary and secondary surgery for the presence of LNM (OR 0.97; 95% CI 0.49 to 1.93; p=0.940) and recurrence during follow-up (HR 0.97; 95% CI 0.41 to 2.34; p=0.954). Further adjusting for lymphovascular invasion, depth of invasion and number of retrieved lymph nodes did not alter this outcome.ConclusionsOur data do not support an increased risk of LNM or recurrence after secondary surgery compared with primary surgery. Therefore, an attempt for an en-bloc resection of a possible T1 CRC without evident signs of deep invasion seems justified in order to prevent surgery of low-risk T1 CRC in a significant proportion of patients.

Objectives:The decision to perform secondary surgery after endoscopic resection of T1 colorectal cancer (CRC) depends on the risk of lymph node metastasis and the risk of incomplete resection. We aimed to examine the incidence and risk factors for incomplete endoscopic resection of T1 CRC after a macroscopic radical endoscopic resection.Methods:Data from patients treated between 2000 and 2014 with macroscopic complete endoscopic resection of T1 CRC were collected from 13 hospitals. Incomplete resection was defined as local recurrence at the polypectomy site during follow-up or malignant tissue in the surgically resected specimen in case secondary surgery was performed. Multivariate regression analysis was performed to analyze factors associated with incomplete resection.Results:In total, 877 patients with a median follow-up time of 36.5 months (interquartile range 16.0–68.3) were included, in whom secondary surgery was performed in 358 patients (40.8%). Incomplete resection was observed in 30 patients (3.4%; 95% confidence interval (CI) 2.3–4.6%). Incomplete resection rate was 0.7% (95% CI 0–2.1%) in low-risk T1 CRC vs. 4.4% (95% CI 2.7–6.5%) in high-risk T1 CRC (P=0.04). Overall adverse outcome rate (incomplete resection or metastasis) was 2.1% (95% CI 0–5.0%) in low-risk T1 CRC vs. 11.7% (95% CI 8.8–14.6%) in high-risk T1 CRC (P=0.001). Piecemeal resection (adjusted odds ratio 2.60; 95% CI 1.20–5.61, P=0.02) and non-pedunculated morphology (adjusted odds ratio 2.18; 95% CI 1.01–4.70, P=0.05) were independent risk factors for incomplete resection. Among patients in whom no additional surgery was performed, who developed recurrent cancer, 41.7% (95% CI 20.8–62.5%) died as a result of recurrent cancer.Conclusions:In the absence of histological high-risk factors, a ‘wait-and-see’ policy with limited follow-up is justified. Piecemeal resection and non-pedunculated morphology are independent risk factors for incomplete endoscopic resection of T1 CRC.