Background: In this study, we aimed to investigate the lymph node standardized uptake value (SUVmax)/mass SUVmax ratio for the determination of sensitivity of positron emission tomography-computed tomography (PET-CT) in mediastinal lymph node staging in patients with non-small cell lung cancer (NSCLC).

Methods: A total of 31 patients (3 female, 28 males; mean age 61.0±9.2 years; range 35 to 79 years) with pathologically confirmed diagnosis of NSCLC in Süreyyapaşa Chest Diseases and Thoracic Surgery Training and Research Hospital, 9th Chest Diseases Clinic between January 2007 and October 2010 were included. These patients underwent PET-CT and mediastinoscopy for staging. The mass SUVmax/lymphadenomegaly (lymph node) SUVmax ratios were determined by comparing the primary mass SUVmax with the PET-CT SUVmax value of lymph node with mediastinoscopy-confirmed pathological diagnosis. The reliability of these ratios in detecting metastasis was assessed by dividing the ratios into three groups using the 1.5 and 2.5 cut-off values.

Results: No statistically significant difference was found between patients with positive lymph node results and those with negative results with regards to the mass SUVmax levels (p>0.05). The lymph node SUVmax levels of patients with positive lymph node pathology results were found to be statistically significantly higher than in patients with negative pathology results (p<0.01). The relationship of lymph node positive pathology with mass SUVmax/lymph node SUVmax was found to be statistically significant (p<0.01). The rate of the mass SUVmax/ lymph node SUVmax ratio between 0 and 1.5 in patients with positive pathology results was found to be higher, whereas the rate of mass SUVmax/lymph node SUVmax ratio to be ≥2.5 in patients with negative pathology results was found to be higher.

Conclusion: Our study results showed that the mass SUVmax/lymph node SUVmax ratio viewed on PET-CT is correlated with mediastinal metastasis in patients with NSCLC. We also demonstrated that the false positivity on PET-CT significantly increased in patients with a cut off ratio value was >2.5.

Keywords : Diagnosis of metastasis; mediastinal lymph node standardized uptake value; non-small cell lung cancer; positron emission tomography-computed tomography