Evaluation of the 7^th and 8^th editions of the AJCC/UICC TNM staging systems for lung cancer in a large North American cohort

Purpose: The new 8^th American Joint Committee on Cancer (AJCC)/International Union for Cancer Control (UICC) lung cancer staging system was developed and internally validated using the International Association for the Study of Lung Cancer (IASLC) database, but external validation is needed. The goal of this study is to validate the discriminatory ability and prognostic performance of this new staging system in a larger, independent non-small cell lung cancer (NSCLC) cohort with greater emphasis on North American patients.

Methods: A total of 858,909 NSCLC cases with one malignant primary tumor collected from 2004 to 2013 in the National Cancer Database (NCDB) were analyzed. The primary coding guidelines of the Collaborative Staging Manual and Coding Instructions for the new 8^th edition AJCC/UICC lung cancer staging system was used to define the new T, M and TNM stages for all patients in the database. Kaplan-Meier curves, Cox regression models and time-dependent receiver operating characteristics were used to compare the discriminatory ability and prognostic performance of the 7^th and the revised 8^th T, M categories and overall stages.

Results: We demonstrated that the 8^th staging system provides better discriminatory ability than the 7^th staging system and predicts prognosis for NSCLC patients using the NCDB. There were significant survival differences between adjacent groups defined by both clinical staging and pathologic staging systems. These staging parameters were significantly associated with survival after adjusting for other factors.

Conclusions: The updated T, M, and overall TNM stage of the 8^th staging system show improvement compared to the 7^th edition in discriminatory ability between adjacent subgroups and are independent predictors for prognosis.