FDG PET/CT for assessing the resectability of NSCLC patients with N2 disease after neoadjuvant therapy

Neoadjuvant chemoradiotherapy (CMRT) is the most effective treatment of stage III non-small-cell lung cancer (NSCLC). The present study aimed at assessing FDG PET/CT for defining the response of N2 disease to neoadjuvant CMRT, as surgical resection after such therapy significantly improves 5-year survival in responding N2 disease.

Forty-five patients with locally advanced NSCLC underwent both pre-neoadjuvant therapy FDG PET/CT and post-neoadjuvant therapy FDG PET/CT followed by anatomical resection of lung and ipsilateral mediastinal lymph nodes (LN). Seventeen of these patients who had PET/CT studies in our institution and were operated after CMRT were retrospectively included in the study group (12 males, ages 43-78 years; stage IIIA: 14 patients, stage IIIB: 3 patients). PET/CT response in N2 was visually scored per-lymph node station and per patient. Quantitative N2 response was evaluated by SUVmax and total lesion glycolysis (TLG) measurements after therapy alone and in comparison with pre-therapy values. PET/CT N2 response was confirmed at surgery.

Seventeen NSCLC patients with 29 metastatic N2 lymph nodes (LN) were assessed. Histopathology confirmed 14 responders and 3 non-responders, and was available in 20/29 metastatic LN, showing complete response in 17 and residual disease in 3 LN. LN-based visual analysis of N2 response on PET/CT defined 3 TP, 16 TN and 1 FP, for sensitivity, specificity, accuracy, negative and positive predictive values (NPV and PPV) of 100, 94, 95, 100 and 75%, respectively. Patient-based visual analysis defined 3 TP, 13 TN and 1 FP study, for sensitivity, specificity, accuracy, NPV and PPV of 100, 93, 94, 100 and 75%, respectively. Nodal-based quantitative analysis of FDG uptake in N2 nodes revealed a significant difference between responding and non-responding LN only of SUVmax post-therapy (2.5 ± 1.21 vs. 3.5 ± 2.36, P = 0.04).

FDG PET/CT after neoadjuvant therapy accurately defined response in metastatic N2 nodes of NSCLC patients, presenting very high sensitivity and NPV for detecting responding nodes. PET/CT may enable selection of candidates for curative resection of stage III NSCLC. Mediastinoscopy may not be mandatory in patients with a negative PET/CT after neoadjuvant therapy.