32. Endoscopic polypectomy for malignant polyps: outcome and predictors of lymph node spread

Abstract

Background Invasive malignancy is present in 0.5-8.3% of colorectal polyps detected at colonoscopy. NHMRC guidelines recommend surgery for patients with adverse histological features (lymphovascular invasion or poor differentiation) or close ( Aim To evaluate outcome in patients with malignant polyps at a tertiary referral centre that utilises NHMRC guidelines and compare with histological features. Method Polypectomy specimens with invasive adenocarcinoma from 2004 to 2012 were identified and cross referenced with a prospective endoscopic database. Cases where endoscopic polypectomy was reportedly complete were selected and reviewed by two GI pathologists. Follow up data including surgical resection reports was evaluated to determine outcomes. Results 51 cases (26 males and 25 females) with a mean age of 66 were identified. Nineteen had a single adverse feature (14 close margin, 1 poor differentiation, 4 lvsi), 11 had two adverse features (8 close margin and lvsi, 1 poor differentiation and lvsi, 2 poor differentiation and close margin). No case showed all three adverse features. Thirty-two patients had surgery (4 without adverse histological features); no residual disease was present in any case but lymph node metastasis was seen in 4 cases. All 4 cases had lvsi with three also having close polypectomy margins. Conclusions 1. Lymphovascular invasion is a strong predictor of nodal metastasis in malignant polyps. 2. Margin clearance and poor differentiation appear less predictive of nodal metastasis. 3. In high risk surgical candidates there may be a role for close observation where a clearance margin