Tumor, Node, and Metastasis Classification: 8th Edition Changes

The 8^th Edition of the Tumor, Node and Metastasis (TNM) classification of lung cancer will help clinicians refine prognosis and help researchers stratify tumors in clinical trials, but will also require more attention to tumor size, nodal disease, and searching for metastases, according to a report presented at the International Association for the Study of Lung Cancer (IASLC) 17^th Annual World Conference on Lung Cancer in Austria.¹

The innovations introduced in the 8^th Edition are based on the analyses of the new IASLC database that includes 70,967 evaluable patients with non-small cell lung cancer (NSCLC) and 6189 with small cell lung cancer (SCLC).

Tumor size is now included as a descriptor in all tumor categories, and this indicates that small changes in size imply important changes in prognosis, said Ramon Rami-Porta, MD, of the Hospital Universitari Mutua Terrassa in Barcelona, Spain, who delivered the report.

In part-solid tumors, only the solid or invasive part will be used to measure tumor size. Minimally-invasive adenocarcinomas now have their own coding in the TNM classification to increase physician awareness. “Together with the smallest coded solid tumors, these can become the base from which to study therapeutic options,” said Dr Rami-Porta.

There are no changes in nodal categorization in the new edition, but Dr Rami-Porta noted that quantification of nodal disease does have prognostic implications. The 8^th Edition indicates that more nodal stations indicate a worse prognosis, and that involvement of multiple N1 stations is similar to that of tumors with single station N2.

Metastasis classification includes new categories for extrathoracic metastases, including M1b for single and M1c for multiple extrathoracic metastases. “The fact that single extrathoracic metastases have their own category will facilitate the redefinition of oligometastatic and oligoprogressive disease, the establishment of therapeutic protocols with radical intention, and the investigation of all therapeutic modalities to eliminate the advanced disease,” said Dr Rami-Porta. “Clinical staging will have to be precise and will have to determine the number and the organ location of the metastatic deposits.”

Other changes include moving some TNM subsets from 1 stage to another and the creation of new stages and sub-stages to accommodate groups of tumors with similar prognoses. 

Reference

1. Rami-Porta R. Lung cancer staging – changing the clinical practice. Paper presented at: International Association for the Study of Lung Cancer 17^th World Conference on Lung Cancer; December 2016; Vienna, Austria.