Indications for invasive mediastinal staging in patients with early non-small cell lung cancer staged with PET-CT

Purpose/Objective(s): Appropriate use of invasive mediastinal staging in patients with clinically node-negative NSCLC staged by PET-CT is critical in selecting patients for curative-intent therapy such as surgery or SBRT, but little data exists to guide this decision-making. We examined a large population of patients with clinical stage I NSCLC referred for mediastinoscopy or EBUS to find risk factors for occult N2 lymph nodes and determine which patients benefit from invasive staging. Materials/Methods: We identified consecutive clinical T1-2N0 NSCLC patients being evaluated for curative intent therapy between 2011 and 2015. None had evidence of nodal disease by PET-CT; the endpoint was pathologic confirmation of occult N2 disease by EBUS or mediastinoscopy. Tumor size, location, histology, SUVmax, and radiographic appearance were evaluated as determinants of occult N2 disease. Two group comparisons of continuous variables were done with independent t-tests and categorical variables were compared with chi(2) or Fisher's exact test. Results: In 284 patients with PET-CT-staged clinical T1-2N0 disease, the prevalence of occult N2 metastases was 7.0%. The negative predictive value of PET-CT was 92.9% and the negative predictive value of mediastinoscopy/ EBUS was 96.3%. T2 tumors were more likely to have occult N2 disease than T1 tumors (11.8% v 3.6% p = 0.009). Pure solid tumors had greater involvement of N2 nodes than tumors with any ground glass component (12.6% v 3.1%, p < 0.001). 17.5% of central tumor cases were found to have occult N2 metastases while 4.4% of patients with peripheral tumors (P < 0.001). 33.3% of patients with solid central T2 tumors had occult N2 metastases whereas 2.0% of patients with peripheral T2 tumors with a ground glass component, 1.2% of patients with peripheral T1 tumors with a ground glass component and 3.6% of patients with peripheral T1 solid tumors had N2 metastases. Conclusions: Invasive mediastinal staging should be strongly encouraged in central tumors and solid T2 tumors because the risk of occult nodal involvement is greater than 10% in these cohorts. However, for patients with peripheral T1 tumors or peripheral T2 tumors with a significant ground glass component, the yield of invasive staging after a negative PET-CT is very low and invasive staging may not be warranted.