Accuracy of positron emission tomography and computed tomography (PET/CT) in detecting nodal metastasis according to histology of non-small cell lung cancer

Positron emission tomography and computed tomography (PET-CT) is the non-invasive gold standard method for determining the oncological stage of patient with diagnosis of lung cancer. A correct preoperative staging is significant because only patients who do not have a history of regional or distant disease are those who will benefit from a surgical treatment. However, due to the different values of the PET-CT in terms of sensitivity and specificity to evaluate the mediastinal lymph node involvement, it is often necessary to perform a surgical mediastinal sampling through a cervical video mediastinoscopy (VM). Patient's risk factors which could modify the results of the PET scan, performing differences between non-invasive staging and the lymph node sampling due to VM are not yet clearly established in the literature. This knowledge will allow to identify in whom a surgical staging by sampling the mediastinal lymph nodes is needed. We included 234 patients with diagnosis of lung cancer who underwent a mediastinal lymph node staging by PET-CT images and histopathological results of mediastinal sampling by VM, analyzing the sensitivity and specificity of this non-invasive imaging study. We also analyzed variables that could modify the results of PET-CT, such as tumor type, location of the tumor and patient's history. We showed that those PET-CT presented an overall sensitivity and specificity of 93.8 and 62.7%, respectively, with negative and positive predictive values of 95.05 and 57.1%, respectively. The false-positive rate was 25% (57 of 234 patients). Analyzing risk factors involved in this false-positive rate (n = 57), we found that the only statistically significant factor that could explain these results was the histology of squamous carcinoma (p < 0.03). In this group of patients, it is essential to perform a mediastinal lymph node biopsy to know the real state of lymph node involvement.