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E07 - Staging in the Molecular Era (ID 7)
- Event: WCLC 2013
- Type: Educational Session
- Track: Imaging, Staging & Screening
- Presentations: 1
E07.2 - Image Interpretation and New Adenocarcinoma-Classification (ID 404)
14:00 - 15:30 | Author(s): K. Garg
There is a widely divergent clinical, radiologic, molecular and pathologic spectrum within lung adenocarcinoma. Remarkable advances in understanding of the genetic mechanisms that underlie lung adenocarcinoma have altered the diagnostic criteria that determine subsequent treatment. The use of the term bronchioloalveolar carcinoma (BAC) encompassed a broad spectrum of tumors ranging from solitary small peripheral lung tumors with a 100% 5-year survival to widespread advanced disease with a 10% 3-5 year survivals, with widely varying use of terminology even after publication of the 2004 WHO Classification. There are also clinical, radiologic, immunohistochemical, and molecular differences that are distinguishable among the subsets of mucinous and non-mucinous types of adenocarcinoma. In 2011, a new Classification of Lung Adenocarcinoma was therefore proposed by the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society. The 2011 classification addressed three important weaknesses in the previous classification. First, it eliminated the term BAC. Second, it added new terminologies of carcinoma-in-situ, and minimally invasive adenocarcinoma to recognize that minimal invasion (< 5mm). Third, it replaced the terminology of mixed adenocarcinoma. The widespread availability of MDCT and abundance of new information obtained especially from low-dose CT lung cancer screening programs, have increased our understanding of the types and management of small peripheral lung nodules encountered in daily clinical practice, in particular, the importance and prevalence of subsolid pulmonary nodules (atypical adenomatous hyperplasia (AAH), ground glass nodules (GGN) and part-solid nodules). Thin section CT has emerged as a new biomarker for lung adenocarcinoma subtypes. The staging system is based solely on the anatomic extent of the disease. Other factors, such as clinical symptoms or molecular biological characterization of the tumor or attenuation of nodules on CT are not factored in the new TNM classification. Increasing T status reflects tumors that are larger or invasive. In lung cancer nodal staging depends on the location of involved nodes (as opposed to the number of nodes). The M descriptor defines the presence or absence of distant metastatic disease. In 2007, The International Association for the Study of Lung Cancer (IASLC) revised the lung cancer stage groupings based on newer survival data. In the 7[th] edition of TNM classification of lung cancer, following modifications were made: (a) Size cut points, in addition to the 3 cm cut point that traditionally separated T1 and T2 tumors, was introduced at 2, 5, and 7 cm. T1 tumors were now subdivided into T1a and T1b around the 2 cm cut point. T2 tumors were subdivided into T2a and T2b around the 5 cm cut point, and tumors larger than 7 cm. were classified as T3. (b) Cases in which additional tumor nodules are found were reclassified. Those in the same lobe as the primary tumor are now classified as T3, those in the other ipsilateral lobes are T4 and those in the opposite lung are now M1a. (c) Cases associated with pleural or pericardial nodules or effusions were reclassified from T4 to M1a. M1 disease due to distant metastasis was reclassified as M1b. A new IASLC nodal chart, with precise definitions was also agreed, reconciling the previous differences between the Japanese and Mountain-Dresler charts. The concept of nodal zones was introduced to make such classification relevant to those dealing with bulky nodal deposits that transgress the boundaries of individual nodal stations. Further improvements in stage discrimination and management of lung cancer could be expected in the future, as more robust data related to genetic make-up and biological behavior affecting survival of tumors becomes available.
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