T. A. (2018). Palatine tonsil SUVmax on FDG PET-CT as a discriminator between benign and malignant tonsils in patients with and without head and neck squamous cell carcinoma of unknown primary. Clinical Radiology.
AbstractAims:18-F-FDG PET/CT is used to identify the primary site in head and neck SCC of unknown primary.Tonsils are an important potential primary however accurately distinguishing physiological from malignant tonsillar uptake can be challenging. We analysed the SUVmax ratio between tonsils in patients with and without tonsillar carcinoma to determine useful diagnostic thresholds.
Materials and Methods:PET/CTs of patients with suspected head and neck SCC and in controls from April 2013 -September 2016 were retrospectively reviewed. Tonsillar SUVmax ratio (ipsilateral/contralateral for malignant tonsils, maximum/minimum for patients without (controls)) was calculated and used to construct a ROC curve.
Results:Twenty-five patients had tonsillar carcinoma: mean, range of the SUVmax ratio was 2.0, 0.89 -5.4.There were eighty-six controls with mean, range of the SUVmax ratio of 1.1, 1 -1.5. Using the ROC, the most accurate SUVmax ratio for identifying malignancy was > 1.2 (77% sensitivity, 86% specificity). A potentially more clinically useful SUVmax ratio is ≥ 1.6 with 62% sensitivity and 100% specificity.
Conclusion:An SUVmax ratio between tonsils ≥ 1.6 is highly suspicious for SCC and could be used to direct site of biopsy. Some malignant tonsils had normal FDG uptake therefore PET/CT should not be used to exclude tonsillar cancer. Minor asymmetrical uptake is frequently seen in non-malignant tonsils and does not necessarily require further investigation. Due to the single centre nature of this study and the recognised variation in SUV measurements between PET scans other centres may need to develop their own cut-offs
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