Revised TNM Classification of Lung Cancer to Offer More Precise Staging

The newly revised 8th edition of the tumor, node, and metastasis (TNM) classification of lung cancer will improve the precision of staging and provide physicians with new data with which to treat patients, according to Ramón Rami-Porta, MD, PhD, of the thoracic surgery service at the Hospital Universitari Mutua Terrassa in Barcelona.

The revised classification system will be published in 2016 by the Union for International Cancer Control (UICC) and the American Joint Committee on Cancer (AJCC). Dr. Rami-Porta presented an overview of proposed changes at the 2015 World Conference on Lung Cancer in Denver, Colorado.

The revisions will be based on data collected by the International Association for the Study of Lung Cancer (IASLC) Staging and Prognostic Factors Committee. IASLC has collected an extensive, international database of lung cancer case information from 94,708 patients diagnosed between 1999 and 2010, including tumor sizes, lymph node involvement, and metastasis.

“The new database is much richer in details to allow refinements in the analysis of the different descriptors,” Dr. Rami-Porta said. “The collaboration of patients and the contributing organizations for this project are crucial to making strides in the study of lung cancer across the globe.”

These data will inform the 8th Edition of the TNM classification of lung cancer.

The IASLC Lung Cancer Staging Project’s proposed changes for T staging were published in July, and proposals for N and M staging were published earlier this month in the Journal of Thoracic Oncology. The proposed recommendations and supporting database will be submitted to the UICC and the AJCC for assessment and inclusion in the new staging manuals, which will be published in 2016 and take effect in January 2017.

“TNM is purely anatomical,” Dr. Rami-Porta emphasized. “It deals with anatomy, and does not contain genetic or clinical factors.”

“In the future, I think we’re going to incorporate genetics-and that’s going to get very complicated,” commented Everett Vokes, MD, John E. Ultmann professor and chair at the department of medicine at the University of Chicago.

The new classification system will address new information about T descriptors, including tumor size.     

“Every centimeter counts. By analyzing the data, we have found T size is an even more important prognosticator than we used to believe,” Dr. Rami-Porta said. “We’ve confirmed that invasion of the diaphragm has poor prognosis-a T4 prognosis. Now, by incorporating tumors larger than 7 cm as T4 and invasion of the diaphragm as T4, we found statistically significant differences in T3 and T4.”

The proposals also reflect analyses of prognostic significance of tumor burden in hilar and mediastinal lymph nodes, and the prognostic impact of number and anatomic location of metastatic tumors.

The proposed changes include classification of a single metastasis in a single distant organ as M1b and classification as M1c cases involving multiple metastatic lesions, whether metastases occur in one or multiple distant organs, Dr. Rami-Porta said.

“The staging of cancer is hallowed by tradition, and for the purpose of analysis of groups of patients it is often necessary to use such a method,” Dr. Rami-Porta said. “The UICC believes that it is important to reach agreement on the recording of accurate information on the extent of disease for each site, because the precise clinical description of malignant neoplasms and histopathological classification may serve a number of related objectives, including to aid the clinical in the planning of treatment; to give some indication of prognosis; to assist in evaluation of the result of treatment; to facilitate the exchange of information between treatment centers; (and) to contribute to the continuing investigation of human cancer.”