Methods: A total of 207 patients with non-small cell lung cancer who were performed positron emission tomography-computed tomography between November 2006 and February 2010 were prospectively analyzed. Of these patients, 143 patients (125 males, 18 females; mean age 62.1 years; range 39 to 85 years) whose invasive staging was performed after positron emission tomography were included in the study. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy rates of positron emission tomography were calculated and compared using a maximum standardized uptake value cut-off value of ≥2.5 and the newly determined maximum standardized uptake value cut-off value.

Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy rates were 45.3%, 78.9%, 55.8%, 71%, and 66.4%, respectively, when the maximum standardized uptake value cut-off value was considered 2.5 in mediastinal lymph nodes. The new maximum standardized uptake value cut-off value was determined to be 4.8 in metastatic lymph nodes. These values were 39.6%, 91.1%, 72.4%, 71.9% and 72%, respectively, according to the new maximum standardized uptake value cut-off value of 4.8. There was a significant difference only between specificity rates when the two different maximum standardized uptake value cut-off values were used (p=0.022).

Conclusion: In this study, the sensitivity of positron emission tomography in the evaluation of mediastinal lymph nodes was lower than those reported in the literature. This situation may be associated with the frequently observed granulomatous infections such as tuberculosis in our country. Results of positron emission tomography should be evaluated according to countries and a new maximum standardized uptake value cut-off value should be calculated particularly for mediastinal lymph node metastasis in multicenter studies in our country.