Published online Jan 16, 2018. doi: 10.4253/wjge.v10.i1.37
Peer-review started: July 28, 2017
First decision: September 11, 2017
Revised: November 4, 2017
Accepted: November 19, 2017
Article in press: November 20, 2017
Published online: January 16, 2018
Upper GI cancer accounts for 4% of cancers diagnosed in the United Kingdom and as such is a significant public health issue. Surgical resection of the primary tumour and any involved lymph nodes results in the best outcomes. For this to be possible however, the surgical team must be confident that the disease is localised. Accurate pre-operative tumour staging is therefore paramount before any decisions regarding treatment are undertaken. In keeping with other organ systems, tumour staging of the upper digestive tract follows the TNM (Tumour, Node, Metastasis) system. The nodal staging of upper GI cancer has been an area of controversy. The 2011 United Kingdom joint medical, surgical and oncology guideline advised that positron emission tomography-computed tomography (PET-CT) imaging should be used in combination with standard computed tomography (CT) and upper GI endoscopic ultrasound (EUS) in the assessment and staging of oesophageal and oesophago-gastric junctional cancer. However in the era of relatively widespread use of PET-CT in this setting, the exact role of EUS remains unclear.
Several studies have assessed the role of PET-CT in the nodal staging of upper GI cancer. Most studies agree that PET-CT has high levels of sensitivity in the detection of malignant mediastinal lymph nodes. However, it is well documented that non-malignant processes such as inflammation can result in false positive findings which will adversely affect the specificity of PET-CT in this setting. The false positive rate of PET-CT has been quoted as between 1.5% and 7.5% in upper GI cancer. It has also been suggested that this may be an underestimate as positive findings are not always evaluated further. We performed this study to evaluate the performance of PET-CT in this setting within our centre and to compare this with the findings from other centres.
The first objective of this project was to evaluate the sensitivity, specificity, positive predictive value and negative predictive value of PET-CT in the detection of malignant mediastinal lymph nodes in the setting of upper GI cancer within the authors’ tertiary referral centre. The second objective was to evaluate the impact on subsequent therapeutic strategy that the addition of EUS-FNA had in these patients.
The authors performed a retrospective review of prospectively recorded data held on all patients with a diagnosis of upper gastrointestinal (GI) cancer made between January 2009 and December 2015. Only those patients who had both a PET-CT and EUS with FNA sampling of a mediastinal node distant from the primary tumour were included.
The authors found that EUS-FNA leads to altered staging of upper GI cancer, resulting in more patients receiving radical treatment that would have been the case using PET-CT staging alone. The authors found that EUS-FNA resulted in altered tumour staging and subsequent management in 25% of cases included in this study. The authors were also interested to find that the rate of concordance of PET-CT and EUS-FNA findings was dependent on the tumour histological subtype. There was a 71.7% rate of concordance in cases with squamous cell carcinoma compared with 61.3% concordance in cases with adenocarcinoma. The reasons for this are unclear and this is therefore an area that requires further study.
The authors suggest that EUS-FNA remains an important diagnostic tool to optimise mediastinal nodal staging in upper GI cancer. Use of this modality ensures that patients are not potentially overstaged by PET-CT, and allows them to be directed to the appropriate therapeutic pathway after MDT discussion. Therefore EUS-FNA appears to have a critical role in confirming whether suspicious nodes identified on PET-CT have malignant involvement, in order to optimise staging of this disease. The authors feel that this is the most significant and clinically relevant finding of this study.
The authors’ findings contrast with several previous studies which reported lower sensitivity but higher specificity rates for the detection of malignant mediastinal lymph nodes by PET-CT. The interpretation of a positive mediastinal lymph node on PET-CT imaging in these studies seems to have been the same as our interpretation in that any FDG uptake beyond background level was considered significant. The reasons for our different findings remain unclear and require further study. The authors also found that the rate of concordance between PET-CT and EUS-FNA findings was greater in patients with squamous cell carcinoma than in those with adenocarcinoma (71.7% and 61.3% respectively). The authors could not find any study which addresses this area in the context of upper GI cancer specifically. This is therefore an area that requires further study.