Can FDG-PET-CT Predict L.N. Capsular Invasion in Metastatic Nodes in Patients with Locoregional Recurrent Differentiated Thyroid Cancer?.

Introduction: To assess the ability of (PET-CT to detect L.N. affection with tumor in differentiated thyroid
cancer, and to assess L.N. capsular invasion which may be an important factor for subsequent locoregional tumor
recurrence.
Ain of work: The 2015 American Thyroid Association (ATA) guidelines state that 18 F-FDG PET-CT is highly
advised for the evaluation of therapy response, the identification of lesions in metastatic disease, and outcome
prediction in high-risk patients who have elevated thyroglobulin levels and negative whole-body iodine scans
(I131). It is not advised as a standard pre-operative scan or for the assessment of thyroid nodules.21
Patients and methods: cross-sectional study included patients admitted to National cancer institute with
recurrent well differtiated thyroid cancer (WDTC) aged between 35 and 70 years. The patients were diagnosed by
elevated thyroglobulin (Tg) level, neck U.S., or C.T. Then FDG- PET CT was performed to assess regional recurrence
and level of SUV nodal activity. Resection of recurrence was performed, and pathological results were obtained.
Results: in the 15 patients who did PET- CT it was able to detect nodal metastasis in all of the 15 patients, with
all of them had pathologically proven nodal metastasis. 11 patients out of the 15showed nodal activity of 10 SUV
or more, with three of them showed nodal activity of 10 or more in their second nodal metastasis. All patients with
nodal activity of 10 SUV or more showed L.N.s capsular invasion with the tumor.
Conclusion: 18- FDG- PET CT may be an important tool for detection of locoregional WDTC recurrence, the
diagnose of L. Ns affection and infiltration nodal capsule. It seemed that SUV activity was related more to tumor
biology, activity, and the presence of tumor infiltration of L.N capsule. It seemed that SUV activity of 10 or more
may be indicator of L.N. capsular invasion, and hence correlated with more incidence of recurrence.