Background Accurate assessment of mediastinal lymph nodes is crucial in determining the management strategies in patients with lung cancer, particularly in those suitable for radical treatment. Positron emission tomography/computed tomography (PET-CT) is currently the best available imaging tool to assess nodal involvement and current guidelines recommend further sampling of PET positive lymph nodes to confirm the diagnosis using image-guided or surgical techniques to achieve the best treatment outcomes. We proceeded to look at the accuracy of (18) F-FDG PET/CT in detecting nodal metastasis in lung cancer.

Methods Retrospective study of 68 pathologically confirmed metastatic lymph nodes obtained using endobronchial ultrasound (EBUS) guided needle aspiration between Jan 2009 and Jan 2012. All pre-procedure PET/CT images were reviewed by a Consultant Radiologist who was blinded to the EBUS findings and the pathology results. PET standardised uptake value (SUVmax) of the primary lung lesion and suspected lymph nodes was measured. Data was collected from our EBUS database and analysed.

Results Of the 68 lymph nodes, 24 were subcarinal, 14 right lower paratracheal, 6 left lower paratracheal, 2 upper right paratracheal, 1 right inter-lobar, 10 right hilar and 11 were left hilar. EBUS lymph node size (mm) 18 mean, SD 6 (range 7 34). Mean PET SUVmax of the lymph nodes was 9.1, 6.7 SD (2 34); mean PET SUVmax of the primary tumour (n = 50) was 10.6(7.6 SD). 23 nodes were squamous, 17 nodes adenocarcinoma, 9 small cell, 13 non-small cell (not otherwise specified), 5 extra-thoracic, and 1 neuroendocrine. 52 nodes were positive on PET, 9 were negative and 7 indeterminate.

Conclusion Our results show that out of the 68 pathologically confirmed lymph nodes 52 were positive on PET/CT with diagnostic accuracy of 76%. SUVmax may be used as a guide to characterise the nodes but not as a confirmatory tool. Despite limitations PET/CT is accurate and it is complemented by image-guided sampling in the lung cancer diagnostic pathway.

References 1. Guidelines on the radical management of patients with lung cancer, Thorax 2010;65(Suppl III):iii1eiii27

2. NICE clinical guideline 121, Lung cancer: The diagnosis and treatment of lung cancer, April 2011