A Critique of the International Association for the Study of Lung Cancer Lymph Node Map: A Radiation Oncology Perspective

Accurate assessment of nodal involvement is essential in the management of lung cancer. Recently, the International Association for the Study of Lung Cancer (IASLC) Lung Cancer Staging Project published a new lymph node map with the aim of creating an internationally agreed framework that would allow precise and uniform determination of lymph node status by centers around the globe.1 This new map contains important changes to the previously used Mountain-Dresler2 and Naruke3 maps. Conformal radiotherapy planning requires accurate delineation of target volumes. Although there is debate regarding the merits of elective versus involved mediastinal nodal irradiation,4–6 accurate outlining of nodal groups is essential regardless for both prognostication and treatment delivery. Nodal stations are usually outlined as contiguous volumes on computed tomography (CT) scans of the chest, and this generally requires complete and precise descriptions of the anatomical limits to be outlined. Atlases have been created to assist with this task and aim to provide comprehensive guides regarding station boundaries (e.g., Chapet7). We feel that the new IASLC map contains some ambiguities from the viewpoint of radiotherapy planning and outline these here in the hope of promoting discussion that clarifies how radiation oncologists should implement the IASLC map.