INTRODUCTION

The AJCC 8th edition TNM classification for lung cancer was released in 2017. This edition has made major changes in many tumor descriptors including sites of metastasis. The new staging system has been a subject of multiple validation studies, of which many have had mixed results. The present study is designed to critically evaluate the results of these external validation studies.

METHODS

A metaanalysis of these external validation studies was performed to critically evaluate the new staging system. Out of 12 studies, 8 were found to fulfill the eligibility criteria, with 654,185 patients being included in the analysis. Hazard ratios (HRs) and associated 95% confidence intervals (CI) extracted from these studies were utilized for analysis. The primary outcomes were survival discrimination and prognostic ability of the 8th edition compared with the 7th edition.

RESULTS

The HRs for the 8th edition staging system were 1.41 in IB, 1.64 in IIA, 1.24 in IIB, 1.95 in IIIA, 3.96 in IIIB, and 4.82 in IIIC compared with IA. The new edition fared better than the 7th edition in survival discrimination in all but stage IIA and IIB. The C-index of the 8th and 7th editions was 0.690 and 0.688, respectively, suggesting almost similar prognostic values.

CONCLUSIONS

This study shows that the survival discrimination of the 8th edition fared better than the 7th edition in all but stage IIA and IIB. The prognostic value of the two staging systems is similar, with no added advantage of the new edition.