Low value of second-look endoscopy for detecting residual colorectal cancer after endoscopic removal

Background and Aims: Endoscopic resection is often feasible for submucosal invasive colorectal cancers (T1 CRCs) and usually judged as complete. If histology casts doubt on the radicality of resection margins, adjuvant surgical resection is advised, although residual intramural cancer is found in only 5% to 15% of patients. We assessed the sensitivity of biopsy specimens from the resection area for residual intramural cancer as a potential tool to estimate the preoperative risk of residual intramural cancer in patients without risk factors for lymph node metastasis (LNM). Methods: In this multicenter prospective cohort study, patients with complete endoscopic resection of T1 CRC, scheduled for adjuvant resection due to pathologically unclear resection margins, but absent risk factors for LNM, were asked to consent to second-look endoscopy with biopsies. The results were compared with the pathology results of the surgical resection specimen (criterion standard). Results: One hundred three patients were included. In total, 85% of resected lesions were unexpectedly malignant, and 45% were removed using a piecemeal resection technique. Sixty-four adjuvant surgical resections and 39 local full-thickness resections were performed. Residual intramural cancer was found in 7 patients (6.8%). Two of these patients had cancer in second-look biopsy specimens, resulting in a sensitivity of 28% (95% confidence interval, <58%). The preoperative risk of residual intramural cancer in the case of negative biopsy specimens was not significantly reduced (P =.61). Conclusions: The sensitivity of second-look endoscopy with biopsies for residual intramural cancer after endoscopic resection of CRC is low. Therefore, it should not be used in the decision whether or not to perform adjuvant resection. (Clinical trial registration number: NCT02328664.)