A Few Clouds Over the Eighth Edition T Categorization System
Authors: Ming Li, Zhijie Xu, Cheng Zhan, Qun Wang
Journal: Journal of Thoracic Oncology (2020)

Let me paraphrase Lord Kelvin here: The beauty and clearness of the TNM staging system of lung cancer, which has been regarded as the most precise system for prognosis prediction and highly accepted in clinical practice, is at present obscured by a few clouds. We read carefully with interest the article by Kim et al.1Kim H. Goo J.M. Kim Y.T. Park C.M. Validation of the eighth edition clinical T categorization system for clinical stage IA, resected lung adenocarcinomas: prognostic implications of the ground-glass opacity component.J Thorac Oncol. 2020; 15: 580-588Abstract Full Text Full Text PDF PubMed Scopus (9) Google Scholar In this study, they further validated the clinical T category and evaluated the independent prognostic role of the nodule type. Interestingly, the nodule type was not an independent prognostic factor, whereas cT1c and solid portion size were independent prognostic factors in the part-solid nodule subgroup. As the authors have stated, the critical problem is whether the current clinical T categorization system is suitable for part-solid tumors. This raises the following two (more) questions: how to assess the size of part-solid tumors and whether the ground-glass opacity (GGO) component of a tumor contributes to the prognosis. However, these are controversial. Current studies are now strengthening the view that pure GGO or part-solid nodules dominant with GGO may have a specific particularity with pure-solid tumors, and thus they should be classified in a novel clinical T category, regardless of their radiological size.2Fu F. Zhang Y. Wen Z. et al.Distinct prognostic factors in patients with stage I non-small cell lung cancer with radiologic part-solid or solid lesions.J Thorac Oncol. 2019; 14: 2133-2142Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar,3Mao R. She Y. Zhu E. et al.A proposal for restaging of invasive lung adenocarcinoma manifesting as pure ground glass opacity.Ann Thorac Surg. 2019; 107: 1523-1531Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar Similarly, in the prospective study at our institution, we found that the presence of GGO components was associated with favorable survival, especially for pure GGO nodules (NCT03723629). This observation may have a significant influence on our surgical resection decision. Pathologists have recognized that only the size of a solid component may have aggressiveness. What determines the diagnosis and prognosis should be the invasive component, which is known as the solid component in clinical and pathologic size. Thus, these studies really speak of the development of prognostic models, in which GGO dominance may now be a strong determinant. One thing we have to be crystal clear about is that the TNM stage is based on anatomy, and we cannot mix different parameters, such as clinical factors, nodule or histologic subtype, or information of molecular biology and tumor genetics, particularly biomarkers (EGFR, ALK, etc.), in the system. Nevertheless, we can combine them to build prognostic groups to provide our patients the best assessment and individualized treatment, which is where the TNM staging system really means. In addition, we have the following question: Is the span of 1 cm accurate enough for smaller tumors, such as Tis, T1mi, and T1a? Stage T1 was further subclassified into T1a to T1c on the basis of the size of the cut point for every 1 cm. In many validation studies, no matter how many cases, new T categories had superior abilities to distinguish and identify the different prognostic outcomes of patients, both in the clinical and pathologic stages, which the seventh edition did not possess, especially between stages T3 and T4. Nonetheless, every millimeter may count, and we have to follow up carefully and measure the tumor size accurately. The prognosis may change with the size of the tumor, even if the size increases from 1 cm to 1.1 cm. Finally, the staging of lung cancer with multiple lesions does not seem to have been solved entirely, and the eighth edition staging system has failed to provide accurate prognostic value for lung cancer as a second primary malignancy.4Shi S. Xie H. Yin W. et al.The prognostic significance of the 8th edition AJCC TNM staging system for non-small-cell lung cancer is not applicable to lung cancer as a second primary malignancy.J Surg Oncol. 2020; 121: 1233-1240Crossref PubMed Scopus (3) Google Scholar The road ahead never stops; large-scale prospective and high-quality studies are needed to bring a superior prognosis refinement and stratification of the current TNM staging system. We need to work together to strengthen dialogue, see the unseen, and change the unchanged. This work is supported by the National Natural Science Foundation of the People's Republic of China (grant no. 81672268) (www.nsfc.gov.cn/). Validation of the Eighth Edition Clinical T Categorization System for Clinical Stage IA, Resected Lung Adenocarcinomas: Prognostic Implications of the Ground-Glass Opacity ComponentJournal of Thoracic OncologyVol. 15Issue 4PreviewThere is controversy regarding the clinical T (cT) category of lung adenocarcinomas that manifest as part-solid nodules (PSNs). We aimed to validate the cT category and to evaluate the independent prognostic role of the nodule type (i.e., part-solid versus solid). Full-Text PDF Open Access