Recursive partitioning for new classification of patients with esophageal cancer treated by chemoradiotherapy.

e14500 Background: The 7th edition of the American Joint Committee on Cancerstaging system does not include lymph node size in the guidelines for staging patients with esophageal cancer. The objectives of this study were to determine the prognostic impact of the largest lymph node diameter (ND) on survival and to develop and validate a new staging system for patients with esophageal squamous cell cancer who were treated with definitive chemoradiotherapy (CRT). Methods: Information on 402 patients with esophageal cancer undergoing CRT at 2 institutions was reviewed. Univariate and multivariate analyses of data from 1 institution were used to assess the impact of clinical factors on survival, and recursive partitioning analysis was performed to develop the new staging classification. To assess its clinical utility, the new classification was validated using data from the second institution. Results: According to RPA, ND stages were best when classified as ND0 (the absence of lymph node metastases), ND1 (< 2...