Are Ratio of Lymph Node to Primary Focus SUV- max and PET/CT FDG Standard Uptake Value of Lymph Nodes Meaningful in Staging Non-Small Cell Lung Cancer?

Surgical treatment for mediastinal lymph node involvement in non-small cell lung cancer (NSCLC) will not have positive impact on survival. The present study aimed at investigating the role of positron emission tomography/computerized tomography (PET/CT) in staging NSCLC. Ninety-nine patients with maximal standard mediastinal lymph node involvement value (SUVmax) of 2.5 or more on PET/CT scanning were included in this study. All patients underwent invasive staging or pathological staging with direct thoracotomy. Relationship between lymph node SUVmax and lymph node/primary mass SUVmax ratio and presence of lymph node metastasis was investigated. Mean SUVmax ratio was 3.87 in the group with positive mediastinal lymph node on PET/CT but pathologically benign lymph nodes whereas it was 5.69 in those with pathologically malignant lymph nodes. Although there was a numeric difference between two groups, the difference was statistically insignificant (p= 0.65). Lymph node/mass SUVmax ratio was 0.49 in the patients with positive lymph nodes on PET/CT and benign pathology whereas it was 0.65 in those with malignant pathology and the difference between them was found to be not significant (p= 0.61). It was observed, however, that as SUVmax ratio increased, possibility of detecting malignant lymph node raised. Rate of malignancy was 52.38% in the group with SUVmax ratio of 0.1 to 0.3 whereas it was 91.66% in those with SUVmax ratio of 1 or greater. No significant relationship was found between lymph node SUVmax rate and presence of metastatic lymph node. We believe that more multi-center studies are needed with more patients.