Proposed revision of the 8th edition AJCC clinical staging system for esophageal squamous cell cancer treated with definitive chemo-IMRT based on CT imaging

PURPOSE: To validate and propose revision of the 8th edition American Joint Committee on Cancer (AJCC) clinical staging system for esophageal squamous cell cancer (ESCC) patients treated with definitive intensity-modulated radiation therapy combined with concurrent chemotherapy (Chemo-IMRT) based on computed tomography (CT) imaging. METHODS: The clinical data of patients with ESCC treated with Chemo-IMRT were collected and retrospectively reviewed. All CT images were independently reevaluated and restaged according to the 8th edition AJCC staging system. The overall survival (OS) rates were analyzed statistically. ROC curves of the various parameters of the primary tumor and metastatic lymph nodes were generated in order to identify the cutoff values correlated to patient survival using the area under curve. RESULTS: The gross tumor volume of the primary tumor (GTV-prT) and the clinical N stage (cN) were independent factors that influenced OS. The 5-year OS rate of patients with GTV-prT ≤28 cm(3), GTV-prT > 28 and ≤ 56 cm(3), and GTV-prT > 56 cm(3) were 54.6, 31.1 and 18.6%, respectively. The 5-year OS rate of patients with cN0, cN1 SLNM (−), cN2 SLNM (−), cN3 SLNM (−) and SLNM (+) were 62.8 (P < 0.001), 34.0 (P = 0.16), 20.0 (P = 0.785), 0 (P < 0.001) and 26.9%, respectively. After restaging the SLNM as regional MLNs, the 5-year OS rates of the patients with cN0, 1, 2 and 3 were 62.8, 36.3, 23.7 and 7.8%, respectively. Various GTV-prT were combined with the cN to establish a new clinical TNM staging system: I, GTV-prT1 and cN0; II, GTV-prT2 or 3 and cN0, GTV-prT1 and cN1; III, GTV-prT1 and cN2, GTV-prT2 and cN1,2; Iva, GTV-prT3 and cN1,2; IVb, GTV-prT(any) and cN3; IVc, T(any)N(any)M1. Subsequently, the OS differed significantly between the adjacent GTV-prT cN categories, except those of stage I vs. II. CONCLUSION: The SLNM should be dealt with as a regional rather than a distant disease in patients with ESCC when treated with CRT. The proposed nonsurgical staging system based on the GTV-prT and N appears to be a simple and accurate prognosis predictor for patients with ESCC who have undergone definitive Chemo-IMRT.