MS27.04 Therapeutic Implications of AJCC 8th Edition T1 Subsets

Abstract

In January 2018, the American Joint Committee on Cancer (AJCC)/International Union for Cancer Control (UICC) introduced the 8thedition of the tumor, node, and metastasis (TNM) staging system for lung cancer. In the 7thedition, T1a tumors were defined as <2cm and T1b tumors were defined as 2-3cm. In preparation for the 8thedition, an analysis was done of the International Association for the Study of Lung Cancer (IASLC) database and statistically significant differences in survival based on tumor size in increments of 1cm were found (1). Thus, the 8thEdition T-stage was divided into three subgroups: T1a, tumor 1cm or less; T1b, tumor more than 1cm but not larger than 2cm; T1c, tumor more than 2cm but not larger than 3cm. Currently, the standard of care for early stage lung cancer is surgical resection by lobectomy, based on the results of the 1995 Lung Cancer Study Group trial showing improved survival compared with sublobar resection (2). With improvements in imaging technology and clinical staging, the question of whether sublobar resection, in the form of wedge resection or segmentectomy, can provide an oncologically equivalent treatment remains to be answered (3). In a comparison of survival between lobectomy and sublobar resection, it was found that the survival benefit from lobectomy was only present for patients before 1997 and not for the newer cohorts (4). This suggests that early stage lung cancer patients of the present era are different from the era by which our current standards of care were established. Similarly, in comparing outcomes after lobectomy with sublobar resection using the T-stage from the AJCC/UICC 7thedition, there was no difference in survival based on the type of resection for T1a and T1b ground glass-predominant nodule groups, although there was a higher rate of lymph node metastases in the T1b group (5). Additionally, Okada et al found that there was no difference in survival between lobectomy or segmentectomy for T1a tumors based on the AJCC/UICC 7thedition classification (6). Thus, even when using the prior classification of T-stage, there is evidence to suggest that these early tumors should be managed differently than larger, more advanced non-metastatic tumors. With the introduction of the AJCC/UIC 8thedition of the staging system, further studies will be able to better delineate the question of whether sublobar resection is appropriate for early stage lung cancer and whether a specific size cutoff within the T1 stage can guide the extent of resection. 1. Rami-Porta R, Bolejack V, Crowley J, Ball D, Kim J, Lyons G, et al. The IASLC Lung Cancer Staging Project: Proposals for the Revisions of the T Descriptors in the Forthcoming Eighth Edition of the TNM Classification for Lung Cancer. J Thorac Oncol. 2015;10(7):990-1003. 2. Ginsberg RJ, Rubinstein LV. Randomized trial of lobectomy versus limited resection for T1 N0 non-small cell lung cancer. Lung Cancer Study Group. Ann Thorac Surg. 1995;60(3):615-22; discussion 22-3. 3. Van Schil PE. Non-small cell lung cancer: the new T1 categories. F1000Res. 2017;6:174. 4. Yendamuri S, Sharma R, Demmy M, Groman A, Hennon M, Dexter E, et al. Temporal trends in outcomes following sublobar and lobar resections for small (≤ 2 cm) non-small cell lung cancers--a Surveillance Epidemiology End Results database analysis. J Surg Res. 2013;183(1):27-32. 5. Tsutani Y, Miyata Y, Nakayama H, Okumura S, Adachi S, Yoshimura M, et al. Appropriate sublobar resection choice for ground glass opacity-dominant clinical stage IA lung adenocarcinoma: wedge resection or segmentectomy. Chest. 2014;145(1):66-71. 6. Okada M, Mimae T, Tsutani Y, Nakayama H, Okumura S, Yoshimura M, et al. Segmentectomy versus lobectomy for clinical stage IA lung adenocarcinoma. Ann Cardiothorac Surg. 2014;3(2):153-9. lung cancer, Surgical resection, TNM 8th Edition