Outcomes of colonoscopic polypectomy for malignant adenomas: a prospective 30‑year cohort study from a single center

INTRODUCTION Surgery is recommended following endoscopic polypectomy for malignant adenoma (MA) in the large bowel in patients with risk factors for tumor recurrence or distant metastasis are present.

OBJECTIVES We present long‑term outcomes of a prospective study in patients with endoscopically removed MAs.

PATIENTS and METHODS A total of 128 patients who underwent endoscopic polypectomy were followed up for a median of 70.4 months. The criteria for adequate polypectomy included endoscopically and histologically (margin ≥2 mm) complete excision, lack of angioinvasion, and good tumor differentiation (G1 or G2). Sixty‑seven patients did not meet 1 or more of the criteria (high‑risk group) and 61 met all of the criteria (low‑risk group). Unfavorable outcomes were residual disease, lymph node metastasis, recurrent disease, distant metastasis, or death due to colorectal cancer. Histological samples from 85 patients were reassessed to determine the effect of a margin width of 1 mm or more and tumor budding on the outcomes.

RESULTS Surgery was performed in 36 patients (28.1%), of whom 32 (47.7%) were high‑risk and 4 (6.5%) were low‑risk. Unfavorable outcome was observed in 10 patients (7.8%; all high‑risk; 10 of 67 patients, 14.9%). Favorable outcome was observed in 61 of 128 patients who had a 2‑mm free margin, and in 44 of 85 patients who fulfilled the modified criterion of 1‑mm free margin. Tumor budding was detected in 17 of 85 patients (20.9%). Unfavorable outcome was observed in 2 of these patients (11.7%) and in 5 patients (7.3%) without tumor budding (P >0.05).

DISCUSSION Long‑term outcomes of an endoscopic resection of MAs are good. Bowel resection does not prevent unfavorable outcomes, while a reduction of the tumor‑free margin would not deteriorate the results.