Risk factors for lymph node metastasis in T1 esophageal squamous cell carcinoma: A systematic review and meta-analysis

BACKGROUND: Lymph node metastasis (LNM) affects the application and outcomes of endoscopic resection in T1 esophageal squamous cell carcinoma (ESCC). However, reports of the risk factors for LNM have been controversial. AIM: To evaluate risk factors for LNM in T1 ESCC. METHODS: We searched Embase, PubMed and Cochrane Library to select studies related to LNM in patients with T1 ESCC. Included studies were divided into LNM and non-LNM groups. We performed a meta-analysis to examine the relationship between LNM and clinicopathologic features. Odds ratio (OR), mean differences and 95% confidence interval (CI) were assessed using a fixed-effects or random-effects model. RESULTS: Seventeen studies involving a total of 3775 patients with T1 ESCC met the inclusion criteria. After excluding studies with heterogeneity based on influence analysis, tumor size (OR = 1.93, 95%CI = 1.49-2.50, P < 0.001), tumor location (OR = 1.46, 95%CI = 1.17-1.82, P < 0.001), macroscopic type (OR = 3.17, 95%CI = 2.33-4.31, P < 0.001), T1 substage (OR = 6.28, 95%CI = 4.93-8.00, P < 0.001), differentiation (OR = 2.11, 95%CI = 1.64-2.72, P < 0.001) and lymphovascular invasion (OR = 5.86, 95%CI = 4.60-7.48, P < 0.001) were found to be significantly associated with LNM. Conversely, sex, age and infiltrative growth pattern were not identified as risk factors for LNM. CONCLUSION: A tumor size > 2 cm, lower location, nonflat macroscopic type, T1b stage, poor differentiation and lymphovascular invasion were associated with LNM in patients with T1 ESCC.