Validation of the post-neoadjuvant staging system of the American joint committee on cancer, 8th edition,in patients treated with neoadjuvant chemoradiotherapy followed by curative esophagectomy for localized esophageal squamous cell carcinoma

ObjectiveThe American Joint Committee on Cancer 8th edition staging system presents separate classifications for pTNM and post-neoadjuvant ypTNM (ypTNM-8th) to enhance prognostic prediction after neoadjuvant therapy and surgery. We aimed to validate the ypTNM-8th staging system and to compare the prognostication performance of ypTNM-8th with that of pTNM-7th and pTNM-8th in esophageal squamous cell carcinoma (ESCC) patients receiving neoadjuvant chemoradiotherapy (nCRT).MethodsWe reviewed 207 ESCC patients treated with nCRT between January 2007 and December 2014 and compared the Akaike information criterion (AIC) and Harrell's C-index to determine the prognostic performance of each TNM system.ResultsSurvival curve analysis of pTNM-7th and -8th showed a stepwise drop in survival from ypT0N0 to advanced stages, whereas the survival outcome of ypStage III showed a better prognosis than that of ypStage II according to ypTNM-8th. Lymphovascular invasion, perineural invasion, and tumor regression grade were significantly associated with overall survival on univariate analysis. Each TNM system showed significant p-values for trend (p < 0.0001 each), but after adjusting for prognostic factors, ypTNM-8th did not significantly predict survival (p = 0.15), whereas pTNM-7th remained significant (p < 0.001). pTNM-7th incorporating ypT0N0M0 and ypT0 (is)N + M0 as separate groups was superior in prognostication as its AIC was smaller and its C-index was higher than those of pTNM-8th and ypTNM-8th, respectively.ConclusionsBecause ypTNM-8th did not provide sufficient prognostication for patients with ESCC treated with nCRT followed by esophagectomy, more sophisticated prognostic classification should be developed for the ypTNM staging system in these patients.