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Lymph Nodes in Lung CancerLymph Nodes in Lung Cancer: Location?: Location, Location, and Location? FREE TO VIEW

Valerie W. Rusch, MD, FCCP
Author and Funding Information

From Thoracic Service, Department of Surgery, Memorial Sloan-Kettering Cancer Center.

CORRESPONDENCE TO: Valerie W. Rusch, MD, FCCP, Thoracic Service, Department of Surgery, Miner Family Chair in Intrathoracic Cancers, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; e-mail: ruschv@mskcc.org


FINANCIAL/NONFINANCIAL DISCLOSURES: The author has reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;147(5):1203-1204. doi:10.1378/chest.14-2767
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In this issue of CHEST (see page 1299), Lee and colleagues1 examine the validity of a mapping system for lymph nodes proposed by the International Association for the Study of Lung Cancer (IASLC). They conclude that the definitions for the anatomic location of lymph nodes in the IASLC map accurately predict disease-free survival in patients undergoing resection of non-small cell lung cancer. In a secondary analysis, they suggest that lymph ratio (ie, the number of lymph nodes with metastatic disease over the total number of lymph nodes removed) is an independent prognostic factor for survival. How are these observations relevant to our daily clinical practice, and should we be recording the number of involved lymph nodes rather than anatomic location?

The development of the IASLC lymph node map2 was prompted by difficulties encountered in analyses performed for preparation of the seventh edition of the International Staging System for Lung Cancer.3,4 For the first time, these analyses used a very large international lung cancer database derived from cancer registries and clinical trials around the world.5,6 Analyses undertaken to determine whether the descriptors for lymph node involvement should be modified7 brought to light discrepancies in nomenclature between the Naruke map used by the Japan Lung Cancer Society8 and the Mountain-Dresler/American Thoracic Society map used in North America and Europe, especially with respect to the separation of N1 and N2 lymph nodes in the subcarinal and right paratracheal regions.9 Thus, a lung cancer classified in one system as N2, stage IIIA could be classified as N1, stage II in the other system, leading to differences in survival analyses, prognosis, and clinical management. Based on literature review and expert opinion consensus, the proposed IASLC lymph node map reconciled these differences in nomenclature and provided very precise definitions of anatomic location for each lymph node level. Importantly, the anatomic locations can be clearly identified by CT scan, allowing this map to be easily used for clinical as well as pathologic staging.2 In the future, systematic use of this map should lead to better patient selection for clinical trials and more accurate analyses of treatment outcomes. However, proposed changes in lung cancer staging always need external validation before achieving wide acceptance into daily clinical practice. This retrospective study by Lee and colleagues,1 performed on a large cohort of surgically well-staged patients with non-small cell lung cancer, supports some of the key features of the IASLC lymph node map with respect to the changes of classification between hilar (N1) and right paratracheal (N2) lymph node location.

A number of studies, referenced by Lee and colleagues,1 have tried to determine whether the number of metastatic lymph nodes, recorded either as an absolute number or as a lymph node ratio, predicts survival better than anatomic location of involved nodes. The staging systems for several other solid tumors (eg, breast, colon, and melanoma) use the number of metastatic lymph nodes to establish N category and overall tumor stage. In the seventh edition of the international cancer staging systems,3,4 new evidence about the factors predicting overall survival in esophageal cancer led to a switch from lymph node location to the number of metastatic lymph nodes, thereby harmonizing the staging systems for esophagus and stomach. However, to date in lung cancer, analyses have failed to show that lymph node number supersedes anatomic location as a prognostic factor. Analyses of the IASLC database did show, though, that the number of involved levels of lymph nodes (ie, single vs multiple station N1 or N2), and, hence, the burden of locoregional metastatic disease, correlated with survival.7 In addition, it is still difficult to assess the number of metastatic lymph nodes clinically in lung cancer even with contemporary imaging studies and endobronchial ultrasound. For pathologic staging, accurate counting of involved lymph nodes assumes that the surgeon is doing a complete lymph node dissection, is removing nodes whole rather than in fragments, and is labeling nodes individually for the pathologist. This standard of surgical practice is rarely attained. Thus, at present, both scientific evidence and the considerations of routine clinical practice support continuing to use lymph node location rather than the number of metastatic nodes to determine nodal and overall stages. Ongoing analyses of an expanded IASLC lung cancer database, not yet published, suggest that lymph node location will remain the method of assessing N category in the upcoming eighth edition of the international cancer staging systems.

It is important that future studies continue to address this issue of what constitutes the best approach for lymph node staging in lung cancer because it directly affects the daily care of patients and the use of potentially effective but also morbid adjuvant therapies. Lee and colleagues1 have added a nicely performed study to the published literature. More evidence on this topic is needed.

References

Lee S, Lee HY, Lee KS, et al. Change of the junctions between stations 10 and 4 in the new International Association for the Study of Lung Cancer lymph node map: a validation study from a single tertiary referral hospital experience. Chest. 2015;147(5):1299-1306.
 
Rusch VW, Asamura H, Watanabe H, et al. The IASLC Lung Cancer Staging Project: A proposal for a new international lymph node map in the forthcoming seventh edition of the TNM classification for lung cancer. J Thorac Oncol. 2009;4(5):568-577. [CrossRef] [PubMed]
 
American Joint Committee on Cancer. AJCC Cancer Staging Manual.7th ed. New York, NY: Springer; 2010.
 
International Union Against Cancer. TNM Classification of Malignant Tumours.7th ed. Oxford, England: Wiley-Blackwell; 2009.
 
Goldstraw P, Crowley JJ. The International Association for the Study of Lung Cancer international staging project on lung cancer. J Thorac Oncol. 2006;1(4):281-286. [CrossRef]
 
Goldstraw P, Crowley J, Chansky K, et al; International Association for the Study of Lung Cancer International Staging Committee; Participating Institutions. The IASLC Lung Cancer Staging Project: proposals for the revision of the TNM stage groupings in the forthcoming (seventh) edition of the TNM classification of malignant tumours. J Thorac Oncol. 2007;2(8):706-714. [CrossRef] [PubMed]
 
Rusch VW, Crowley J, Giroux DJ, et al. The IASLC Lung Cancer Staging Project: Proposals for the revision of the N descriptors in the forthcoming seventh edition of the TNM classification for lung cancer. J Thorac Oncol. 2007;2(7):603-612. [CrossRef] [PubMed]
 
The Japan Lung Cancer Society. Classification of Lung Cancer.First English ed. Tokyo, Japan: Kanehara & Co; 2000.
 
Mountain CF, Dresler CM. Regional lymph node classification for lung cancer staging. Chest. 1997;111(6):1718-1723. [CrossRef] [PubMed]
 

Figures

Tables

References

Lee S, Lee HY, Lee KS, et al. Change of the junctions between stations 10 and 4 in the new International Association for the Study of Lung Cancer lymph node map: a validation study from a single tertiary referral hospital experience. Chest. 2015;147(5):1299-1306.
 
Rusch VW, Asamura H, Watanabe H, et al. The IASLC Lung Cancer Staging Project: A proposal for a new international lymph node map in the forthcoming seventh edition of the TNM classification for lung cancer. J Thorac Oncol. 2009;4(5):568-577. [CrossRef] [PubMed]
 
American Joint Committee on Cancer. AJCC Cancer Staging Manual.7th ed. New York, NY: Springer; 2010.
 
International Union Against Cancer. TNM Classification of Malignant Tumours.7th ed. Oxford, England: Wiley-Blackwell; 2009.
 
Goldstraw P, Crowley JJ. The International Association for the Study of Lung Cancer international staging project on lung cancer. J Thorac Oncol. 2006;1(4):281-286. [CrossRef]
 
Goldstraw P, Crowley J, Chansky K, et al; International Association for the Study of Lung Cancer International Staging Committee; Participating Institutions. The IASLC Lung Cancer Staging Project: proposals for the revision of the TNM stage groupings in the forthcoming (seventh) edition of the TNM classification of malignant tumours. J Thorac Oncol. 2007;2(8):706-714. [CrossRef] [PubMed]
 
Rusch VW, Crowley J, Giroux DJ, et al. The IASLC Lung Cancer Staging Project: Proposals for the revision of the N descriptors in the forthcoming seventh edition of the TNM classification for lung cancer. J Thorac Oncol. 2007;2(7):603-612. [CrossRef] [PubMed]
 
The Japan Lung Cancer Society. Classification of Lung Cancer.First English ed. Tokyo, Japan: Kanehara & Co; 2000.
 
Mountain CF, Dresler CM. Regional lymph node classification for lung cancer staging. Chest. 1997;111(6):1718-1723. [CrossRef] [PubMed]
 
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