444. SHOULD T2 ESOPHAGEAL SQUAMOUS CELL CARCINOMA BE SUBCLASSIFIED WITH RESPECT TO LYMPH NODE INVOLVEMENT AND SURVIVAL?

Whether T2 esophageal squamous cell carcinoma should be subclassified into circular muscle (T2a) and longitudinal muscle (T2b) remains controversial. We aimed to investigate the effect of the depth of muscularis propria invasion on the incidence of lymph node involvement and patient survival outcomes in T2 esophageal squamous cell carcinoma. We identified patients with pT2 esophageal squamous cell carcinoma who underwent primary surgery from January 2009 to June 2017. The pathological information of the depth of muscularis propria invasion was reassessed, and patients were grouped into the T2a group and T2b group. Binary logistic regression was used to determine risk factors for lymph node metastases. The impact of the depth of muscularis propria invasion on survival was investigated using Kaplan–Meier analysis and a Cox proportional hazard regression model. This study included a total of 750 patients from three institutes. The depth of muscularis propria invasion (OR: 3.95, 95% CI: 2.46–6.35; P < 0.001) was correlated with lymph node metastases using logistic regression. T substage (OR: 1.37, 95% CI: 1.05–1.79; P < 0.001) and N status (OR: 1.51, 95% CI: 1.05–2.17; P < 0.001) were independent risk factors in multivariate Cox regression analysis. The T2a group had better overall survival (OR: 1.52, 95% CI: 1.19–1.94; P = 0.001) than the T2b group, specifically in T2N0 patients (OR: 1.38, 95% CI: 1.08–1.94; P = 0.035). The depth of muscularis propria invasion should be subclassified to T2a and T2b with respect to lymph node involvement and survival outcomes in T2 esophageal squamous cell carcinoma.