Endoscopic resection alone as a potential treatment method for low-risk deep invasive T1 colorectal cancer

Although T1b (deep submucosal invasion) is described as an indication of surgical resection with lymph node dissection for T1 colorectal cancer (CRC) in current guidelines, it reportedly has a weaker correlation to the lymph node metastasis (LNM) than other risk factors (lymphovascular invasion, poorly differentiated or mucinous adenocarcinoma, and tumor budding). "Low-risk T1b" CRC, which is defined as a lesion with only T1b and no other risk factors, may not require additional surgical resection. The aim of this study was to evaluate the necessity of surgeries in patients with low-risk T1b CRC from the point of the risk of LNM, recurrence, and long-term outcome.

From April 2001 to March 2019, a total of 1271 T1 CRCs were resected. Invasion depth and tumor budding were diagnosed according to the Japanese guideline, lymphovascular invasion was evaluated with special staining and immunostaining, and histologic grade was diagnosed by the highest differentiation. A total of 354 patients with low-risk T1b CRC were then analyzed. Among these, 105 patients were resected endoscopically without surgical resection (ER-alone group), and 249 patients were resected surgically (SR group). The rate of LNM, the cumulative recurrence, and overall survival (OS) were examined in each group.

No LNM was observed in either the ER-alone group (0%; 95% CI, 0-4.2) or the SR group (0%; 95% CI, 0-1.8). Five-year cumulative recurrence rate was 0% (95% CI, 0-9) in the ER-alone group and 0% (95% CI, 0%-3%) in the SR group. The 5-year OS rate was 93% (95% CI, 90-96) in the ER-alone group and 95% (95% CI, 93-96) in the SR group (P = .35).

ER alone without SR could be a potential treatment method for patients with low-risk T1b CRC.