Central tumor location and presence of occult lymph node metastasis in cT1N0M0 NSCLC

Abstract

Background and Objective: Recent guidelines on non-small cell lung cancer (NSCLC) propose that tumors smaller than 3 cm, centrally located, without evidence of positive lymph nodes on computed tomography (CT) and/or positron emission tomography (PET) require invasive mediastinal staging by surgical or needle technique before further treatment. The objective of this study was to identify a definition of central location for cT1N0M0 NSCLC that best discriminates the risk of occult mediastinal nodal disease (pN2). Methods: Our institutional pulmonary oncology database was researched for the 2014 to 2017 period for all patients who had cT1N0M0 probable NSCLC after CT and PET-CT. Patients who did not undergo invasive lymph node evaluation were excluded. Two definitions of central location were explored 1) inner third or 2) inner two thirds of the lung field, using a model of concentric circles originating from the hilum. Results: Two hundred and ten cT1N0M0 NSCLC were included in our study after applying exclusion criteria. Twenty-one (10%) and sixty-three (30%) tumors were respectively considered central using the inner third and the inner two-thirds definitions. Central location was not associated with an increased incidence of pN2 using either definition (p = 0.24). Occult pN2 was found in 5.2% of patients (0-4.8% of central tumors versus 5.4-5.8% of peripheral tumors). Higher SUV and female gender were associated with more occult lymph node metastasis. Conclusion: None of the definitions of central location explored were associated with increased prevalence of pN2. pN2 prevalence was low in cT1N0M0 NSCLC and necessity for invasive mediastinal staging in this population should be questioned.