External Validation of the New International Association for the Study of Lung Cancer Tumor, Node, and Metastasis 8th Edition Staging System and Updated T Descriptors in Determining Prognosis for Patients With Non–Small Cell Lung Cancer Patients With N3 Disease

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Abstract

Objective

The objective of this study is to externally validate the 8th Edition of the Tumor, Node, and Metastasis staging system and its updated T descriptors in patients with non–small cell lung cancer with N3 disease.

Methods

Data were extracted from the Surveillance, Epidemiology, and End Results database. Chi-square test, Kaplan–Meier method, and Cox regression models were used in SPSS 23.0 (IBM Corp, Armonk, NY).

Results

A total of 7732 patients with non–small cell lung cancer with T1-4N3M0 disease from 1988 to 2013 were identified. A total of 1410 patients (18.2%) had T1N3 disease, 2491 patients (32.2%) had T2N3 disease, 1563 patients (20.2%) had T3N3 disease, and 2268 patients (29.3%) had T4N3 disease. The 5-year overall survival (OS) for the entire cohort was 8.4%. There was a significant difference in OS concerning T stage (T1N3: 10.8% vs. T2N3: 8.3% vs. T3N3: 8.1% vs. T4N3: 7.3%; P < .001). When stratified by the median age of patients (66 years), a significant difference in OS by stage of disease (IIIB vs. IIIC) was still observed in both the younger (P < .001) and older (P < .001) patient populations. A significant difference in disease-specific survival (DSS) was observed by T stage (T1N3: 14.7% vs. T2N3: 11.6% vs. T3N3: 11.3% vs. T4N3: 9.7%; P < .001). On multivariate analysis, T stage, year of diagnosis, age, gender, histology, and receipt of radiotherapy remained independent prognostic factors for both OS and DSS.

Conclusions

The 8th Edition of the Tumor, Node, and Metastasis staging system significantly stratifies both overall and DSS between stages IIIB and IIIC among those with N3 disease. However, small absolute differences in 5-year outcomes between T stage may suggest limited clinical relevance.

Micro-Abstract

The objective of this study is to externally validate the 8th Edition Tumor, Node, and Metastasis staging system and its updated T descriptors in patients with non–small cell lung cancer with N3 disease. Our analysis suggests that the new staging system statistically stratifies outcomes between stages IIIB and IIIC in those with N3 disease. However, small absolute differences in 5-year outcomes between T stage perhaps suggest limited clinical relevance.

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