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 (RIC) is found in only 5% to 15% of patients. We assessed sensitivity of biopsies from the resection area for RIC as a potential tool to estimate the preoperative risk of RIC in patients without risk factors for lymph node metastasis (LNM).
In this multicenter prospective cohort study, patients with complete endoscopic resection of a T1-CRC, scheduled for adjuvant resection due to pathologically unclear resection margins, but absent risk factors for LNM, were asked to consent for second-look endoscopy with biopsies. The results were compared with pathology results of the surgical resection specimen (criterion standard).
One hundred three patients were included. In total, 85% of resected lesions were unexpectedly malignant, and 45% removed using a piecemeal resection technique. Sixty-four adjuvant surgical resections and 39 local full-thickness resections were performed. RIC was found in 7 patients (6.8%). Two of these patients had cancer in second-look biopsies, resulting in a sensitivity of 28% (95% CI, <58%). The preoperative risk of residual intramural cancer in case of negative biopsy specimens was not significantly reduced (p = 0.61).
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. https://clinicaltrials.gov/show/NCT02328664.

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