Does Omitting Additional Surgery After Local Resection Affect Oncological Outcomes in Patients with High-Risk pT1 Colorectal Cancer?

Introduction: Colorectal cancer (CRC) is a leading cause of cancer-related mortality in Spain, with pT1 adenocarcinomas often managed via endoscopic polypectomy (EP). Determining the necessity of additional surgery post-EP remains challenging, especially given the low incidence of intramural residual tumor (IRT) and lymph node metastasis (LNM) in certain high-risk cases. This study aims to evaluate histological factors predicting residual disease and to explore strategies to reduce unnecessary completion surgeries.

Methods: We analyzed data from 276 patients with pT1 CRC arising from colonic and upper rectal polyps treated with complete EP at our institution between 2013 and 2021. pT1-polyps with positive resection margins, deep submucosal invasion ≥ 2 mm, presence of lymphovascular invasion, high-grade tumor budding, unfavorable histology, or indeterminate polyps were considered high-risk pT1-polyps. Patients were stratified into low-risk (LR), high-risk endoscopic management (HR-E), and high-risk surgical management (HR-S) groups. Follow-up involved clinical, endoscopic, and imaging surveillance over a median of 70 months. IRT, LNM, recurrence, and survival outcomes were analyzed.

Results: Of the 276 patients, 88 (32%) were low-risk managed endoscopically, while 188 (68%) exhibited high-risk features; 128 underwent surgery (HR-S), and 60 were managed with surveillance (HR-E). Residual disease was identified in 18.7% of surgical specimens. IRT was predominantly associated with positive margins (p = 0.01). Unfavorable histology was strongly linked to LNM (p = 0.000). Recurrence rates were similar between HR-E and HR-S groups in patients with a single risk factor, with local recurrences effectively managed surgically. No CRC-specific deaths occurred in the HR-E group, and overall survival was better among patients with lower ASA scores and favorable histology.

Conclusion: Positive resection margins and unfavorable histology are significant predictors of IRT and LNM in pT1 CRC. Careful patient selection and vigilant follow-up may allow safe deferral of completion surgery in selected high-risk patients, especially those with comorbidities or a single histological risk factor, thereby reducing surgical morbidity without compromising survival.