Nuclear medicine

Positron emission tomography PET/ CT is routinely utilized to investigate lymph node (LN) metastases in non-small cell lung cancer. However, it is less sensitive in normal-sized LNs. This study was performed in order to define the prevalence of mediastinal LN metastases discovered on combined endosonography by endobronchial ultrasound (EBUS) and endoscopic ultrasound (EUS) fine needle aspiration in patients with a radiologically normal mediastinum Accurate staging of the mediastinum is critical in the pre-operative staging of non-small cell lung cancer patients.

PET/ CT is routinely utilize

Few studies have evaluated the role of endoscopic staging in non-small cell lung cancer ;(NSCLC) patients with radiologically normal mediastinum. These studies have focused mainly on endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). There are no studies describing the role of combined endosonographic staging by endobronchial ultrasound (EBUS) and endoscopic ultrasound (EUS); guided fine needle aspiration in patients with radiologically normal mediastinum on Computed Tomography (CT) and Positron Emission Tomography Computed Tomography (PET – CT) scans.

The overall rate of unsuspecte N2 disease that is not detect by PET-CT has been report to be between 5% and 15%. CT and PET-CT scans have improve radiological staging of lung cancer; however, these techniques can not provide definitive tissue diagnosis and are associate with high false positive rates and low sensitivities and specificities. EBUS-TBNA allows access to stations 1, 2R, 2L, 3P, 4R, 4L, 7, 10R, 10L, 11R, 11L, 12R, and 12L.

Improved radiological staging

Recent meta-analyses and multiple studies have shown a pooled sensitivity of EBUS – TBNA for LNs within the reach of EBUS is in the range of 88% to 93%. The negative predictive value is 91%. Endoscopic ultra sound guided fine-needle aspiration (EUS-FNA) allows access to stations 2R, 2L, 3P, 4L, 7, 8, 9, celiac axis; left lobe of the liver, and left adrenal gland. In select cases; the AP window lymph nodes (Station 5) and Para-Aortic lymph nodes (Station 6) can also be access by EUS. The
right adrenal gland  also be reach using a transduodenal approach.

The 4R lymph node station can also; be reached by EUS when the nodes are large enough (typically >2 cm). EUS is extremely helpful in assessing the inferior mediastinum and structures below the diaphragm. The sensitivity; specificity, positive predictive value, and negative predictive value of EUS-FNA for LN within the reach of EUS have been reported to be 89%, 100%, 100%, and 86%, respectively.

Combined endosonographic lymph node staging should be consider in the pre-treatment staging of high risk patients with non-small cell lung cancer in the presence of radiologically normal mediastinal lymph nodes due to the significant rate of radiologically occult lymph node metastases