Materials and Methods: The study included 510 cases selected according to the criteria identified between January 2009 and July 2011. PET-CT staging and thorax-CT, size of lymph nodes, histological type of tumor, mediastinal lymph nodes taken and the pathological results were assessed.
Results: SUVmax cut-off value was taken as 2.5 for the metastatic analysis of lymph nodes in PETCT and N1 and N2 lymph node stations were evaluated. Sensitivity for the N2 lymph node stations, was 74.7%, specificity 49.4%, Positive Predictive Value 25.4%, Negative Predictive Value 89,.5% and accuracy 54.1% (p < 0.001). Following the statistical analysis, the new SUVmax cut-off value for the N1 lymph node groups was calculated as 3.34, and for N2 lymph node groups 5.6. Based on the new SUVmax cut-off value for N2 lymph node groups, the sensitivity of PET-CT was calculated as 43.2%, specificity 94.4%, PPV 64.1%, NPV 87.8% and accuracy 84.9% (p < 0.001).
Conclusions: Calculating a new cut off value of SUVmax all around the world would increase the NPV of PET-CT and so it would reduce to use of invasive methods. PPV of PET-CT is still not at an acceptable level, so positive results of PET-CT for mediastinal lymph node staging should be confirmed with invasive diagnostic techniques.
