ECE2015 Guided Posters Thyroid – diagnosis (9 abstracts)
Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Republic of Korea.
Objective: 18F-FDG-avid differentiated thyroid cancers (DTC) have been known to behave more aggressively, especially in metastatic sites (flip-flop phenomenon). However, the clinical behaviour of DTC detected incidentally by FDGPET (PET incidentaloma) has been sparsely reported. We wanted to know whether flipflop phenomenon is applicable in PET incidentalomas.
Methods: 165 DTC patients who underwent thyroid surgery and had pre-operative FDGPET examination at Chonnam National University Hwasun Hospital between January 2006 and August 2013 were included in the study. We compare the clinical characteristics between screening PETCT group (thyroid incidentaloma) and staging PETCT group.
Results: 129 DTC patients were FDG-avid and 36 patients non-FDG-avid. FDG avid PTC is more aggressive than FDG non-avid PTC on the clinico-pathologic findings. After removal of high-risk group (staging PETCT group), thyroid PETCT incidentaloma patients (n=107) were compared according to FDG avidity. Among thyroid PETCT incidentaloma patients, FDG avid PTC group (n=75) revealed larger tumour size (0.97±0.52 vs 0.61±0.35, P=0.001), but extrathyroidal invasion (ETI), cervical lymph node metastasis, and distant metastasis is not different between FDG avid PTC group and FDG non-avid PTC group. A cumulative risk of cervical lymph node metastasis according to primary tumour size of FDG avid PTC group is not different from those of FDG non-avid PTC group (P=0.394).
Conclusions: DTC detected with FDG-avidity do not seem to behave aggressively, based on initial operative findings. FDG-avidity of DTC does not add to conventional risk factor assessment for initial therapeutic decision.