Introduction EUS+/- FNA is commonly used in the nodal staging of upper GI, lung and other malignancies, but the increasing availability of PET-CT has led to a reduction in its use in some centres. However the accuracy of PET-CT in staging mediastinal nodes in particular is unclear. Our aim was to analyse the concordance of PET-CT and EUS+FNA in the staging of mediastinal nodes in malignant disease in one tertiary referral centre.

Methods Electronic reports for all patients attending for EUS between January 2009 and December 2012 were reviewed. Patients who had both mediastinal node sampling and a PET-CT were included for analysis. Using a positive EUS+FNA result as a definitive diagnosis of lymph node involvement, the accuracy, sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of PET-CT in the staging of mediastinal lymph nodes were calculated. The final staging pathway and patient outcomes were also analysed.

Results A total of 77 nodes in 74 patients were sampled (51M, 23F; median age 66). The primary diagnosis was that of oesophageal cancer in 56 patients (38 adeno and 18 squamous); lung cancer in 11 patients; gastric cancer in 3 patients and other malignancies in 4 patients. The FNA cytology results were positive, negative and indeterminate in 32 (42%), 39 (51%) and 6 (8%) cases respectively. The cytological indeterminate nodes were excluded from further analysis. The sampled nodes were positive, negative and indeterminate on PET-CT in 49 (64%), 26 (34%) and 2 (3%) cases respectively. For all patients, the sensitivity, specificity, PPV, NPV and accuracy of PET-CT were 97%, 54%, 63%, 95% and 73% respectively. For the subgroup with oesophageal cancer the sensitivity, specificity, PPV, NPV and accuracy were 94%, 62%, 57%, 95% and 73%. EUS+FNA altered the cancer staging and changed the patient pathway in 14 patients (20%).

Conclusion PET-CT has a poor specificity and PPV for the diagnosis of malignant mediastinal lymph nodes, resulting in a high false positive rate and potential over staging. Therefore EUS-FNA remains an essential part of the staging process for these patients

Disclosure of Interest None Declared.