Risk Factors for Lymph Node Metastasis in Pathological T1b Colorectal Cancer

Background/aim The rate of lymph node metastasis (LNM) of colorectal carcinoma (CRC) with a submucosal (SM) invasion depth of 1000 µm or more can reach 12.5%, which is the most common reason for additional resection in daily practice. Other studies have reported that the rate of LNM is less than 2%, regardless of the depth of invasion, if the lesions show good histology, lymphovascular infiltration is negative, and tumor budding is limited. The purpose of this study was to investigate new risk factors for LNM in T1b colorectal cancer. Patients and methods The 239 patients who were diagnosed with pathological T1b CRC after colorectal surgical resection at the Osaka Police Hospital in Japan between January 2008 and December 2018 were retrospectively reviewed in this study. Results The LNM rate was 11.3% (27/239). The variables identified as being significant factors using multivariate analysis were: i) lymphatic invasion (Ly)-positive [odds ratio (OR)=5.97; 95% confidence interval (CI)=2.27-15.74], ii) female gender (OR=3.49; 95%CI=1.38-8.85), and iii) left-sided colorectal involvement (OR=4.98; 95%CI=1.22-20.39). If none of these risk factors were present with T1b, the LNM rate was 0% (0/28). Conclusions Ly-positive, female gender, and left-sided colorectal involvement could be risk factors for LNM in T1b CRC.