Background: Although a greater depth of tumor invasion is correlated with a poorer prognosis in esophageal squamous cell carcinoma (ESCC), it remains controversial whether T2 ESCC should be subclassified by circular and longitudinal muscle invasion. We conducted a multicenter retrospective study to evaluate the relationship between the depth of invasion and long-term outcome and to identify the clinical significance of subclassifying T2 ESCC.
Methods: Patients with T2 ESCC who underwent esophagectomy at two different institutes between January 2009 and December 2017 were analyzed retrospectively. ESCC with circular and longitudinal muscle invasion was defined as T2 circular and T2 longitudinal ESCC, respectively. Survival outcomes and risk factors for lymph node metastasis (LNM) were evaluated by univariate and multivariate analyses. In addition, data from stage T1b ESCC cases during the same period were retrieved for use as a comparison cohort to evaluate the prognostic significance of the T2 substage.
Results: A total of 536 T2 ESCC patients were eligible, and 192 (36%) patients developed LNM. No significant difference was found in general characteristics between the T2 circular and T2 longitudinal ESCC groups (n = 219 and n = 317, P > 0.05), except for tumor location (P = 0.02). The T2 substage was not significantly correlated with survival on univariate or multivariate analysis (P = 0.30 and P = 0.34, respectively). Multivariate analysis also indicated that the T2 substage was not an independent risk factor for LNM (P = 0.15). When patients with stage T1b ESCC were considered, their survival time was significantly different from that of patients with T2 circular and T2 longitudinal disease (P = 0.01).
Conclusions: The depth of tumor invasion into the circular and longitudinal muscle layers in T2 ESCC does not affect the prognosis or risk of LNM.