Risk of residual tumor following removal of a malignant colorectal polyp with high-risk features.

136 Background: National guidelines recommend surgery when pathology analysis of a colorectal polyp reveals high-risk features: positive margin/piecemeal resection (PM/PR), lymphovascular/perineural invasion (LVI/PNI), poor differentiation (PD), or tumor budding (TB). However, some patients choose to avoid surgery, with its morbidity and quality-of-life implications, despite the risk of residual disease. Methods: This single-center cohort study determined the rates of luminal or lymph node disease and distant metastasis in patients who underwent surgery and patients who underwent observation following removal of a malignant colorectal polyp with high-risk features between 2015 and 2022. Results: Of 336 patients who underwent a polypectomy for a malignant polyp in the colon (n = 226) or rectum (n = 110), 312 had a PM/PR, 96 had LVI/PNI, 47 had PD, and 45 had TB; 208 patients (62%) underwent surgery, and 128 (38%) underwent observation. Patients with a malignant polyp in the rectum were more likely to undergo observation than patients with a malignant polyp in the colon (79 [72%] vs. 49 [22%] patients; P < 0.01). In the surgery group, 19 patients (9%) had residual luminal disease, 39 patients (19%) had lymph node disease, and 5 patients (2%) had distant metastasis. In the observation group, disease was identified in 14 patients (11%): regrowth in the lumen, 7 patients (9%); regrowth in lymph nodes, 5 patients (6%); distant metastasis, 1 patient (1%); regrowth with distant metastasis, 1 patient (1%). The 12 cases of regrowth were salvaged: resection, 4 patients; local excision, 2 patients; chemoradiotherapy, 6 patients. Conclusions: The risk of residual disease following removal of a malignant colorectal polyp with high-risk features is considerable. Patients concerned about the morbidity of surgery and postsurgery quality of life should be counseled about this risk, as well as the availability of effective salvage options. High-risk features (HRF) Surgery(n = 208) Observation (n = 128) Luminal/LN disease at surgery(n = 51; 25%) Luminal/LN regrowth during observation(n = 12; 9.4%) Distant metastasis(n = 7; 2.1%) PM/PR (n = 312; 93%) 193 119 49 (25%) 12 (10%) 7 (2.2%) LVI/PNI (n = 96; 29%) 56 40 16 (29%) 3 (7.5%) 3 (3.1%) PD (n = 47; 14%) 33 14 11 (33%) 0 1 (2.1%) TB (n = 45; 13%) 20 25 5 (25%) 1 (4.0%) 1 (2.2%) 1 HRF (n = 215; 64%) 141 74 31 (22%) 8 (11%) 4 (1.9%) 2 HRF (n = 78; 23%) 39 39 11 (28%) 4 (10%) 1 (1.3%) 3 HRF (n = 35; 10%) 25 10 8 (32%) 0 2 (5.7%) 4 HRF (n = 6; 1.8%) 2 4 1 (50%) 0 0