The role of PET-CT in mediastinal staging of operable non-small cell lung cancer

Aim: Lung cancer is a common cause of cancer releated deaths. Surgery is the most important treatment option in the early stage of non-small cell lung cancer (NSCLC). Positron emission tomography-computed tomography ( PET- CT) is recently used for the preoperative staging. Accurate initial staging is very important at NSCLC especially the mediastinal staging. We aimed to compare results of PET-CT with mediastinoscopy and thoracotomy findings to reveal the effectiveness of PET-CT in mediastinal staging of NSCLC.Materials and methods: 124 patients (107 male, 17 female) diagnosed as operable NSCLC due to preoperative PET-CT scanning performed in our hospital were enrolled in the study. All the clinical and pathological findings were collected retrospectively. For preoperative staging mediastinoscopy was performed in 34 patients, mediastinotomy in 4, thoracotomy for lymph node station 5 in 2 and for lymph node station 7 in 1 patient. Besides 16 patients with negative mediastinoscopy, 83 patients had undergone thoracotomy directly. Postoperative pathology results of lymph node stations of these 99 patients regarding the nodal spread and stage were compared with clinical stage obtained by PET-CT. The sensitivity, specificity, negative (NPV) and positive predictive value (PPV) and accuracy of PET-CT were determined.Results: The sensitivity, specificity, NPV, PPV and accuracy of PET-CT for patients preoperatively staged by invasive methods were determined to be 91.66%, 17.64%, 61.11%, 60% and 60.97%, respectively. For all patients who were considered to be operable these values were found to be 48.27%, 70,37%, 46,66%, 71.69% and 62.65%, respectively and from the aspect of all lymph node stations the results were 34.56%, 93.21%, 43.07%, 90.55% and 85.62%, respectively. The sensitivity, specificity, NPV, PPV and accuracy were 8.1%, 93.49%, 21.42%, 82.29% and 78.15%, respectively for the N1 lymph nodes and 56.81%, 93.08%, 49.01%, 94.85% and 89.28%, respectively for the N2 lymph nodes. Maximum standart uptake (SUVmax) cut-off value for mediastinal N2 involvement in PET-CT was obtained as 3.55. According to the pathological results, with PET-CT T was 47.5% correctly staged, 40.4% downgraded, 12.1% upgraded, while N results were 57.6% the same, 17.1% downgraded and 25.2% upgraded. For the general, correct stage with PET-CT was established in 41.4% of cases while 34.3% was downstaged and 24.2% upstaged.Conclusion: The sensitivity and PPV of PET-CT for mediastinal lymph node staging is low but the specificity and NPV is high. We consider that, when positive mediastinal lymph nodes are detected, invasive mediastinal staging must be performed. On the other hand, patients with negative PET-CT results can be operated upon without invasive mediastinal staging. Compared with N2 nodes, the lower values of sensitivity and PPV for N1 nodes reflects that PET-CT is still insufficient to detect N1 nodes. We obtain better results for clinical nodal staging according to the T and general staging with PET-CT in our hospital.