Incorporation of a Molecular Prognostic Classifier Improves Conventional Non-Small Cell Lung Cancer Staging

Abstract

Introduction: Despite adoption of molecular biomarkers in the management of NSCLC, the recently adopted eighth edition of the TNM staging system utilized only clinicopathologic characteristics and validated improvement in risk stratification of early-stage disease has remained elusive. We therefore evaluated the integration of a clinically validated molecular prognostic classifier into conventional staging.

Methods: A novel staging system, the TNMB (with the B denoting biology) system, which integrates a 14-gene molecular prognostic classifier into the eighth edition of the TNM staging system, was developed by using data from 321 patients with NSCLC at the University of California, San Francisco. The TNMB staging system was subsequently validated in an independent, multicenter cohort of 1373 patients, and its implementation was compared with adoption of the seventh and eighth edition staging systems utilizing metrics of reclassification.

Results: Compared with staging according to the eighth edition of the TNM system, the TNMB staging system enhanced the identification of high-risk patients, with a net reclassification improvement of 0.33 (95% confidence interval [CI]: 0.24-0.41). It better predicted differences in survival, with a relative integrated discrimination improvement of 22.1% (95% CI: 8.8%-35.3%), and it improved agreement between observed and predicted survival, with a decrease in the reclassification calibration statistic of from 39 to 21. The seventh and eighth editions failed to change the net reclassification improvement (0.01 [95% CI: -0.04 to 0.03] and 0.03 [95% CI: 0.00 to 0.06], respectively) or relative integrated discrimination improvement (2.1% [95% CI: -5.8 to 9.9] and -2.5% [95% CI: -17.6 to 12.4], respectively); in addition, the eighth edition worsened calibration, with an increase in the reclassification calibration statistic from 23 to 25.

Conclusions: Incorporation of a molecular prognostic classifier significantly improved identification of high-risk patients and survival predictions compared with when conventional staging is used. The TNMB staging system may lead to improved survival of early-stage disease through more effective application of adjuvant therapy.

Keywords: Eighth edition staging system; Molecular prognostic classifier; Non–small cell lung cancer; Reclassification statistics.