Oncological outcomes after piecemeal endoscopic mucosal resection of large non-pedunculated colorectal polyps with covert submucosal invasive cancer

Abstract

ObjectiveManagement of covert submucosal invasive cancer (SMIC) discovered after piecemeal endoscopic mucosal resection (pEMR) of large (>20 mm) non-pedunculated colorectal polyps is challenging. The residual cancer risk is largely unknown. We sought to evaluate this in a large tertiary referral cohort.DesignCases of covert SMIC following pEMR were identified and followed. Oncological outcomes after surgery were divided based on residual intramural cancer, lymph node metastases (LNM) or both. Risk factors for residual intramural cancer and LNM were analysed based on the original pEMR histological variables. Risk parameters were analysed with respect to low and high-risk variables for residual intramural cancer and LNM.ResultsAmong 3372 cases of large non-pedunculated colorectal polyps, 143 cases of covert SMIC (4.2%) were identified. 109 underwent surgical resection. Histological analysis of pEMR histology was available in 98 of 109 (90%) cases. 62 cases (63%) had no residual malignancy. 36 cases had residual malignancy (residual intramural cancer n=24; LNM n=5; both n=7). All cases of residual intramural cancer could be identified by a R1 histological deep margin. Cases with poor differentiation (PD) and/or lymphovascular invasion (LVI) had a high risk of LNM (12/33), with a very low risk without these criteria (<1%; 0/65). Cases at low risk for LNM with R0 deep margin have a low risk of residual intramural cancer (<1%; 0/35).ConclusionThe majority of cases of large non-pedunculated colorectal polyps with covert SMIC following pEMR will have no residual malignancy. The risk of residual malignancy can be ascertained from three key variables: PD, LVI and R1 deep margin.

A simplified algorithm to evaluate the risk of submucosal invasive cancer in large (≥20 mm) nonpedunculated colonic polyps

“…Furthermore, if the deep margin is clear, despite piecemeal resection, it seems the risk of local recurrence is insignificant. [ 18 ] Optical evaluation of surface vascular and pit patterns of LNPCPs can accurately detect SMIC in flat lesions. The probability of optical evaluation not detecting SMIC in a flat LNPCP was 0.6% in a large prospective study.…”

“…If SMIC is well differentiated with no lymphovascular invasion, the risk of lymph node metastasis is negligible. Furthermore, if the deep margin is clear, despite piecemeal resection, it seems the risk of local recurrence is insignificant [18].…”

Endoscopic Management of Large Non-Pedunculated Colorectal Polyps

“…Until recently, the management of covert SMIC discovered after piecemeal ER has been challenging. A recent observational study (n = 3372) identified 143 (4.2%) cases with covert SMIC post piecemeal resection [48]; 109 cases underwent surgical resection, and 62 (63%) cases had no residual cancer. All cases with residual intramucosal cancer (n = 24) could be identified by a R1 histological deep margin.…”

Endoscopic management of colorectal polyps

“…A lot of work has been done to reduce the recurrence rate. Previous study has concluded that large non-pedunculated colorectal polyps with covert submucosal invasive cancer following piecemeal EMR will have no residual malignancy and the risk of residual malignancy can be ascertained from three key variables: poor differentiation, lymphovascular invasion, and R1 deep margin [ 64 , 65 ] and more meta-analyses have been started to find whether EMR/ESD along with routine margin ablation or snare tip soft coagulation could lower the recurrence rate; thus, these techniques should be considered as standard for endoscopic resection of large colorectal polyps, while CSP, cold EMR, and underwater EMR (UEMR) should only be used within clinical trials pending more high-quality data regarding the local recurrence rate. UEMR has emerged as an alternative method for conventional EMR as the standard modality for removing non-pedunculated colorectal lesions [ 66 ]; an RCT has been conducted to demonstrate a lower recurrence rate and shorter procedure duration by using UEMR.…”