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

Introduction: An international database was collected to inform the 8(th) edition of the anatomic classification of lung cancer. The present analyses concern its primary tumor (T) component. Methods: From 1999 to 2010, 77,156 evaluable patients, 70,967 with non-small-cell lung cancer, were collected; and 33,115 had either a clinical or a pathological classification, known tumor size, sufficient T information, and no metastases. Survival was measured from date of diagnosis or surgery for clinically and pathologically staged tumors. Tumor-size cutpoints were evaluated by the running log-rank statistics. T descriptors were evaluated in a multivariate Cox regression analysis adjusted for age, gender, histological type, and geographic region. Results: The 3-cm cutpoint significantly separates T1 from T2. From 1 to 5cm, each centimeter separates tumors of significantly different prognosis. Prognosis of tumors greater than 5cm but less than or equal to 7cm is equivalent to T3, and that of those greater than 7cm to T4. Bronchial involvement less than 2cm from carina, but without involving it, and total atelectasis/pneumonitis have a T2 prognosis. Involvement of the diaphragm has a T4 prognosis. Invasion of the mediastinal pleura is a descriptor seldom used. Conclusions: Recommended changes are as follows: to subclassify T1 into T1a (1cm), T1b (>1 to 2cm), and T1c (>2 to 3cm); to subclassify T2 into T2a (>3 to 4cm) and T2b (>4 to 5cm); to reclassify tumors greater than 5 to less than or equal to 7cm as T3; to reclassify tumors greater than 7cm 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.