Direction of discordance between PET/CT, EBUS-TBNA, and multidisciplinary tumor board nodal assignment in non-small cell lung cancer

Mediastinal nodal classification in non–small cell lung cancer (NSCLC) at the N0/N1–N2/N3 treatment-defining boundary guides therapeutic strategy and is commonly finalized in multidisciplinary tumor board (MDT) meetings. We compared positron emission tomography/computed tomography (PET/CT) and endobronchial ultrasound–guided transbronchial needle aspiration (EBUS-TBNA) against MDT assignment and quantified discordance at this threshold. We retrospectively analyzed 114 consecutive NSCLC patients who underwent both PET/CT and EBUS-TBNA before MDT review. Nodal stage was dichotomized as N0/N1 vs N2/N3. Because the MDT decision incorporates both modalities, agreement with MDT is reported as observed agreement and Cohen κ together with the direction of discordance, rather than as sensitivity and specificity. In the subgroup with surgical mediastinal staging, both modalities and the MDT category were compared with histopathology. MDT assigned N2/N3 in 84 patients (73.7%). Relative to the MDT category, PET/CT over-classified 16 patients (14.0%) and under-classified 9 (7.9%). EBUS-TBNA under-classified 15 of the 43 patients it classified N0/N1 (34.9%), and under-classification persisted among the 25 patients in whom every sampled station was diagnostic (8/25, 32.0%); 12 of these 15 assignments rested on clinical–radiological course rather than histopathology. Agreement with the MDT category was 85.1% (κ = 0.662) for EBUS-TBNA and 78.1% (κ = 0.389) for PET/CT; because malignant cytology was definitional for the MDT category, 67 of 97 concordant EBUS-TBNA classifications (69.1%) were determined by that rule and do not measure EBUS-TBNA performance. Against surgical histopathology in 18 patients, PET/CT classified 11 of 13 pathologically N0 patients as N2/N3 (specificity 15.4%; 95% CI, 4.3–42.2) and EBUS-TBNA identified 2 of 5 with pathological N2 disease (sensitivity 40.0%; 95% CI, 11.8–76.9). At the treatment-defining nodal boundary, the two modalities diverged from the multidisciplinary decision in opposite directions: PET/CT over-classified nodal status, whereas EBUS-TBNA under-classified in approximately 1 in 3 patients it had assigned N0/N1, including those in whom sampling was complete, although most of these assignments rested on clinical course rather than tissue. These findings are consistent with guideline recommendations that PET-positive mediastinal nodes require tissue confirmation and that a negative endosonographic result be interpreted alongside pretest probability and station coverage.