Introduction
Large non-pedunculated colorectal polyps (LNPCP's) are significant precursors of colorectal cancer, commonly treated by piecemeal endoscopic mucosal resection (pEMR). When histology reveals a focus of adenocarcinoma invading the sub-mucosa, the resection is often considered non curative and salvage surgery is performed. Recent evidence shows that the risk of residual cancer in the bowel wall or lymph nodes of the surgical specimen are uncommon and that in some cases surgery may be avoided even when a focus of invasive cancer is found in the EMR specimen.
Aims & Methods
This is a retrospective observational study aimed to evaluate the prevalence, characteristics, and outcomes of covert carcinoma in LNPCPs resected by EMR in a two academic centers.
Data was collected from a prospective cohort of LNPCPs at two academic centers in Israel. We collected patient, lesion and procedural characteristics prospectively.
EMR was performed by 3 experienced endoscopist with dedicated EMR training. Piecemeal EMR was performed after endoscopic assessment for polyps that were deemed not to have sub-mucosal invasion according to accepted classification systems. Lesions suspected to containing invasive cancer were referred to surgery without endoscopic resection were excluded from the analysis.
For lesions containing invasive carcinoma, data was collected on Kikuchi classification, presence of tumor budding and lymphovascular invasion, grade of tumor differentiation, and status of the deep margin. Surgical data included presence of residual carcinoma in the surgical specimen, grading, margin involvement, and lymph node involvement.
Results
We analyzed 546 LNPCPs referred for resection at the two centers. We identified 27 cases of covert carcinoma, accounting for 4.9% of all LNPCPS resected by piecemeal EMR. A multidisciplinary tumor board deemed resection curative in 7 cases, and 18 patients were refferd for surgical resection. One patient refused surgery, and One patient was lost to follow up.
None of the surgical specimens had lymph node metastasis. In one case residual carcinoma was found in the bowel wall of the surgical specimen. No recurrence of colorectal cancer, presence of metastasis on imaging or elevation of CEA was documented for any of the patients during follow up of two year.
Conclusion
In conclusion, our study shows that covert carcinoma is relatively rare when EMR is performed in a high-volume center by expert endoscopists. In addition, the data suggests that even in these cases, the risk of metastatic disease is probably very low.
References
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Disclosure
Conflicts of interest: None. Financial disclosures: None.