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Old, current lymph node maps inadequately classify lung cancer

Due to inconsistencies in interpretation and application, use of older or newly introduced lymph node maps may reduce the accuracy of stage classification and lead to erroneous management of lung cancer, according to research presented in Chest.

“Accurate and consistent regional lymph node classification (N) is an important element in the staging and multidisciplinary management of lung cancer. Regional lymph node definition sets — lymph node maps — have been created to standardize N,” Ahmed H. El-Sherief, MD, from the Imaging Institute at Cleveland Clinic, and colleagues wrote.

The researchers note that “earlier contemporaneous lymph node maps … were not mutually consistent in their lymph node definition sets, potentially leading to differences in N.”

The International Association for the Study of Lung Cancer (IASLC) created a new lymph node map in 2009 to replace all prior versions; nevertheless, inconsistencies in N standardization of lung cancer still persisted, they wrote.

Between April 2013 and July 2013, El-Sherief and colleagues conducted an online image- and text-based survey to determine how and how often lung cancer specialists use the IASLC lymph node map during lung cancer staging to classify thoracic lymph nodes seen on CT. A total of 337 lung cancer specialists responded to the anonymous 20-question survey which accounted for 25% of specialists who were invited to partake in the survey. Of those, 158 were thoracic radiologists, 102 were thoracic surgeons and 77 were pulmonologists who practice endobronchial ultrasound. 

Survey data indicated that the IASLC lymph node map was used daily by half of all respondents regardless of subspecialty (50%; 95% CI, 44%-55%). The researchers found differences in interpretation and application on CT among IASLC definition sets, especially for lymph nodes near the thoracic inlet and ligamentum arteriosum, anterior to the trachea and tracheal bifurcation, between the bronchus intermedius and esophagus, in the internal mammary space and adjacent to the heart.

“The presence of inconsistencies in lymph node classification among lung cancer specialists indicates that a universally implemented regional thoracic lymph node map has not yet been realized,” El-Sherief and colleagues concluded. “The inconsistencies, ambiguities, and unpredictability introduced by this ad hoc process may be overcome in the future with a lymph node map that simultaneously communicates a standard set of lymph node station definitions in three languages — using the language of anatomic landmarks for surgeons, bronchoscopic landmarks for pulmonologists, and visual CT landmarks for radiologists.” – by Alaina Tedesco

Disclosure: The researchers report no relevant financial disclosures.