Response: A Critique of the International Association for the Study of Lung Cancer Lymph Node Map
Authors: Valerie W. Rusch, Hisao Asamura
Journal: Journal of Thoracic Oncology (2012)

We thank Pitson et al.1Pitson G Lynch R Claude L et al.A critique of the IASLC lymph node map: a radiation oncology perspective.J Thorac Oncol. 2012; 7: 478-480Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar for providing a detailed analysis of the International Association for the Study of Lung Cancer (IASLC) lymph node map from the viewpoint of radiation oncologists. The objectives of this map2Rusch VW Asamura H Watanabe H Members of the IASLC Staging Committee 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: 568-577Abstract Full Text Full Text PDF PubMed Scopus (850) Google Scholar were to reconcile differences between the Japanese and MD-ATS (American Thoracic Society as modified by Mountain and Dresler) maps and to provide more specific anatomic definitions for each of the lymph node stations. Although the map was developed with multidisciplinary input from the IASLC Staging Committee including radiologists and radiation oncologists, additional thoughts are always welcome. We provide a few specific comments in response: 1The authors raise a concern that the anatomic boundaries for stations 1 and 2 lymph nodes may be unclear because of potentially variable location of the clavicle and the apex of the lung (presumably with respiration). In clinical practice, however, the distinction between supraclavicular (station 1) and high paratracheal (station 2) lymph nodes is usually straightforward on physical examination and computed tomography (CT) scan. As station 2 lymph nodes tend to be very close to the midline, their location is static and not prone to variable position with respiration.2We agree with Dr. Pitson that it is important to distinguish between stations 4 and 10 and considerable effort was made to provide clearer definitions in the IASLC map for these stations as well as for station 7. Distal pretracheal lymph nodes are located above the lower border of the azygos vein and are considered 4R and not 10 (Table 1 and Figure 3 in Ref. 2Rusch VW Asamura H Watanabe H Members of the IASLC Staging Committee 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: 568-577Abstract Full Text Full Text PDF PubMed Scopus (850) Google Scholar). The authors are correct that station 7 encompasses a larger area than previously. This change reconciled one of the major differences between the Japanese and MD-ATS maps.3We agree that although separation of stations 8 and 9 is straightforward at surgery, it could be difficult on CT, especially if extensive adenopathy is present. Coronal CT views may be helpful in this regard.4While separation of stations 10 (around the main bronchi) and 11 (interlobar) could conceivably be difficult in situations where there is bulky or confluent N1 disease, these are two anatomically distinct regions that should not be merged routinely. Suggestions for revisions to the IASLC map would certainly be welcomed by the International Staging Committee. However, it is important that such suggestions should recommend specific alternative definitions to anatomical boundaries as they are currently and not merely be critiques. Changes need to be applicable to all disciplines involved in the care of lung cancer patients and be internationally acceptable and meaningful in daily clinical care.