Predictors of mediastinal staging and usefulness of pet in patients with stage IIIa (N2) or IIIb (N3) lung cancer

OBJECTIVE To analyze which factors predict mediastinal N2/N3 lymph node staging and diagnostic accuracy of PET and CT to determine it. PATIENTS AND METHODS We analyzed data collected prospectively in a database that included patients with non-small cell lung cancer (NSCLC) who underwent EBUS-TBNA. Prior to EBUS-TBNA, CT and PET were used to define the radiographic N stage and lymph nodes with short axis ≥ 1 cm by CT or with ratio between maximum standardized uptake value (maxSUV), by PET, of lymph node and primary tumor greater than 0.56, were considered pathological. Definitive lymph node staging was established through EBUS-TBNA, mediastinoscopy or surgical lymph node dissection. RESULTS One hundred and thirty four patients were included, in 88 of whom (65.6%), definitive lymph node staging was N2 or N3. Primary tumor of central location, lymph node size, maxSUV of lymph node and radiographic N stage by CT or PET were associated with N2/N3 in univariate analysis, but in logistic regression model it was only independently related with N stage by CT or PET. Negative predictive value and positive predictive value of CT were 0.81 and 0.74, respectively, and for PET 0.78 and 0.68. CONCLUSION In NSCLC, in locoregional disease radiographic staging by CT or PET predict the existence of N2/N3 mediastinal disease, but negative and positive predictive values of both imaging techniques are not adequate, so EBUS-TBNA samples should be taken in all lymph nodes with a diameter greater than 5 mm, regardless of PET findings.