The IASLC Lung Cancer Staging Project: Proposals for the Revisions of the T Descriptors in the Forthcoming Eighth Edition of the TNM Classification for Lung Cancer

Abstract

Recommended changes are as follows: to subclassify T1 into T1a (≤1 cm), T1b (>1 to ≤2 cm), and T1c (>2 to ≤3 cm); to subclassify T2 into T2a (>3 to ≤4 cm) and T2b (>4 to ≤5 cm); to reclassify tumors greater than 5 to less than or equal to 7 cm as T3; to reclassify tumors greater than 7 cm as T4; to group involvement of main bronchus as T2 regardless of distance from carina; to group partial and total atelectasis/pneumonitis as T2; to reclassify diaphragm invasion as T4; and to delete mediastinal pleura invasion as a T descriptor.

The review of proposals in the forthcoming 8th TNM classification of lung cancer

“…However, instead of classifying patients exclusively according to tumor size, T2 tumors also include tumors classified as T2 by other descriptors other than tumor size, i.e., main bronchus involvement (5). The survival analysis concerning 1-cm increments in tumor size (≤1 cm, >1-2 cm, >2-3 cm, >3-4 cm, >4-5 cm, >5-6 cm, >6-7 cm, and >7 cm) revealed progressive decreases in survival for each 1-cm cut-off.…”

“…Data analysis was performed in 2013-2014. Subsequently, proposals for the revisions were published in the Journal of Thoracic Oncology (5)(6)(7)(8)(9). Finally, it is thought that the 8 th edition of TNM classification will be adopted from 2017.…”

Pros: should a patient with stage IA non-small cell lung cancer undergo invasive mediastinal staging?

“…Stage IA, which involves tumours of 3 cm or less, includes T1a (≤1 cm), T1b (>1 to ≤2 cm) and T1c (>2 to ≤3 cm) tumours in the eight edition of the TNM classification of lung cancer, showing a progressive degradation of survival as tumour size increases (12). European guidelines recommend invasive mediastinal staging in tumours >3 cm, especially in adenocarcinomas.…”

How to deal with subcentimeter lung cancer: a moving target!

“…Besides histology also size matters and this is recognized in the 8 th edition of the TNM classification where the T1 subset will be subdivided into 3 categories with 1 cm cut-off values: T1a will include tumors ≤1 cm, T1b tumors between 1.1-2.0 cm and T1c tumors between 2.1 and 3.0 cm (9). From the large IASLC database it is clear that the smaller tumours have the best prognosis with a 5-year estimated survival rate for clinically and pathologically staged nonsmall cell lung cancers (NSCLC) ≤1 cm without lymph node or distant metastases, of 92% and 91%, respectively.…”