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New Lung Cancer Staging Manual Set to Modify Clinical Practice

In 1998, the International Association for the Study of Lung Cancer (IASLC) established its Lung Cancer Staging Project, which led to the development of an international lung cancer database. The newest edition was described by Ramon Rami-Porta, MD, a thoracic surgeon at Hospital Universitari Mutua Terrrassa in Terrassa, Spain, in early December 2016 at the World Conference on Lung Cancer (Abstract PL03.02). The new 8th edition of the tumor, node, and metastasis (TNM) classification system was published by the Union for International Cancer Control (UICC), the American Joint Committee on Cancer (AJCC), and IASLC in their respective staging manuals. 

According to Dr. Rami-Porta, the 8th edition of the TNM staging manual will help to refine prognosis both at clinical and pathologic staging. However, the new classifications will require more precise measurement of tumor size, use of elastic stains to identify visceral pleural invasion, quantification of nodal disease, determination of the number and location of metastases, with continued use of clinical judgment to select treatment.

Practice-changing modifications have been made to the “T” component of the classification, he said, and tumor size is now a much more relevant prognostic factor than in previous editions. Small changes in size mean important changes in prognosis, he added.

For instance, adenocarcinoma in situ—Tis(AIS)—and minimally invasive adenocarcinoma—T1mi—now have their own coding in the TNM classification, and the smallest solid tumor has been redefined as T1a (≤ 1 cm in largest dimension).

“I think this is an important innovation in the 8th edition because it increases our awareness of the existence of these small tumors, and this may prompt changes in therapy and research,” he said. According to Dr. Rami-Porta, not all small lesions are treated at the time of diagnosis, so growth, density, molecular profile, and genetic signatures of these tumors can be observed over time.

Some TNM subsets have moved from one stage to another, and new stages and substages have been created to accommodate groups of tumors with similar prognoses. The new staging system also provides a set of rules to classify lung cancers with multiple lesions in a homogeneous way.