• Division of Pulmonary and Critical Care, University of Vermont Medical Center, Burlington VT.
• Department of Mathematics and Statistics, University of Vermont, Burlington VT.
• Department of Biomedical Engineering, University of Sao Paulo, Sao Paulo, Brazil.
• Division of Pulmonary and Critical Care, Brigham and Women's Hospital, Boston, MA.
• Department of Radiology, Brigham and Women's Hospital, Boston, MA.
• Division of Pulmonary and Critical Care, University of Vermont Medical Center, Burlington, VT. Electronic address: Matt.Kinsey@med.uvm.edu.

BACKGROUND: Guidelines recommend invasive mediastinal staging for patients with non-small cell lung cancer and a "central" tumor. However, there is no consensus definition for central location. As such, the decision to perform invasive staging largely remains on an empirical foundation.

RESEARCH QUESTION: Should patients with peripheral T1 lung tumors undergo invasive mediastinal staging?

STUDY DESIGN AND METHODS: All participants with a screen-detected cancer with a solid component between 8 and 30 mm were identified from the National Lung Screening Trial. After translation of CT data, cancer location was identified and the X, Y, Z coordinates were determined as well as distance from the main carina. A multivariable logistic regression model was constructed to evaluate for predictors associated with lymph node metastasis.

RESULTS: Three hundred thirty-two participants were identified, of which 69 had lymph node involvement (20.8%). Of those with lymph node metastasis, 39.1% were N2. There was no difference in rate of lymph node metastasis based on tumor size (OR, 1.03; P = .248). There was also no statistical difference in rate of lymph node metastasis based on location, either by distance from the carina (OR, 0.99; P = .156) or tumor coordinates (X: P = .180; Y: P = .311; Z: P = .292). When adjusted for age, sex, histology, and smoking history, there was no change in the magnitude of the risk, and tests of significance were not altered.

INTERPRETATION: Our data indicate a high rate of N2 metastasis among T1 tumors and no significant relationship between tumor diameter or location. This suggests that patients with small, peripheral lung cancers may benefit from invasive mediastinal staging.