IASLC Staging Article
The IASLC Lung Cancer Staging Project: Validation of the Proposals for Revision of the T, N, and M Descriptors and Consequent Stage Groupings in the Forthcoming (Seventh) Edition of the TNM Classification of Malignant Tumours

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Introduction

In 1996, the International Association for the Study of Lung Cancer (IASLC) launched a worldwide TNM staging project to inform the next edition (seventh) of the TNM lung cancer staging system. In this article, we describe the methods and validation approaches used and discuss the internal and external validity of the recommended changes.

Methods

The International Staging Committee agreed on a number of general principles that guided the decision-making process. Internal validity was addressed by visually assessing the consistency of Kaplan-Meier curves across database types, geographic regions and addressing external validity, by assessing the similarity of curves generated using the population-based Surveillance Epidemiology and End Results cancer registry data to those generated using the project database. Cox proportional hazards regression was used to calculate hazard ratios between the proposed stage groupings with adjustment for cell type, sex, age, and region.

Results

Calls for data by the International Staging Committee resulted in the creation of an international database containing information on more than 100,000 cases. The present work is based on analyses of the 67,725 cases of non-small cell lung cancer. Validation checks were robust, demonstrating that the suggested staging changes are stable within the data sources used and externally. For example, suggested changes based on tumor size were well supported, with statistically significant hazard ratios ranging from 1.14 to 1.51 between adjacent pairs in the Surveillance Epidemiology and End Results data.

Conclusions

Lung cancer stage definitions have never been subjected to such an intense validation process. We do accept, however, that this work is limited in ways that can only be addressed by a prospective database, which we intend to develop. In the meantime, we think that this new system will greatly improve the usefulness of TNM lung staging across all of its purposes.

Key Words

TNM classification
Non-small cell lung cancer
Staging validity
International database

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Disclosure: This work was funded by a restricted educational grant from Eli Lilly and Company. No individual from the company had any role in evaluating the data or in preparing the manuscript. The project was also supported by the AJCC grant “Improving AJCC/UICC TNM Cancer Staging.―

A supplementary Appendix of internal validation figures is available via the ArticlePlus feature at www.jto.org. Please go to the August issue and click on the ArticlePlus link posted with the article in the Table of Contents to view this material.