Modification of Nodal Categories in the Seventh American Joint Committee on Cancer Staging System for Esophageal Squamous Cell Carcinoma in Chinese Patients

Background: More data are essential to test the efficacy of the American Joint Committee on Cancer (AJCC) system for staging esophageal squamous cell carcinoma. We tested the classifiers used in the AJCC staging system and propose a modification to this system to better represent the survival characteristics of esophageal squamous cell carcinoma in the Chinese population.

Methods: We used data from two centers, which established the training (n=1,006) and validation (n=783) cohorts. All the patients underwent curative surgical treatment. Survival was compared using AJCC classifiers to test the efficacy of this staging system. Martingale residuals from a Cox proportional hazards regression model were used to modify the nodal categories. The results obtained from the training cohort were validated with the validation cohort at each step.

Results: The evaluation of the patients' overall survival allowed only poor discrimination between AJCC IIIb and IIIc cancers in both cohorts. Also, in both cohorts, N2 and N3 classification cancers could not be well discriminated in terms of survival when AJCC nodal categories were used. Nevertheless, the survival rate could easily be distinguished when using the four modified categories: 0, 1, 2 to 3, and 4 or more positive nodes. The survival difference between IIIb and IIIc obtained using the modified nodal categories could easily be discriminated in both cohorts.

Conclusions: Esophageal squamous cell carcinoma nodal staging for the Chinese population was more accurately classified using the following four categories: no positive node, 1 positive node, 2 to 3 positive nodes, and 4 or more positive nodes. Further studies are required to confirm these results.