Endocrine Abstracts (2017) 49 EP1422 | DOI: 10.1530/endoabs.49.EP1422

Incidental thyroid uptake detected by 68Ga-DOTANOC positron Emission Tomography: is it clinical significant?

Tiago Nunes da Silva1, Joaquim Gomes Santos2, Ana Catarina Matos1, João Pedro Teixeira3, Carla Oliveira4, Joana Castanheira4, Susana Carmona2,5, Hugo Duarte3, Durval Costa4, Luis Oliveira5, Ana Isabel Santos2 & Jorge Portugal

1Endocrinology Department Hospital Garcia de Orta, Almada, Portugal; 2Nuclear Medicine Department Hospital Garcia de Orta, Almada, Portugal; 3Nuclear Medicine Department – IPO Porto, Porto, Portugal; 4Nuclear Medicine department Champalimaud Centre for the Unknown, Lisboa, Portugal; 5Nuclear Medicine Unit – Oncological Centre Dr.a Natália Chaves/Joaquim Chaves Saúde, Carnaxide, Portugal.

Background: The detection of thyroid incidental uptake of radiopharmaceuticals has been increasing. Those detected by 18F-fluorodeoxyglucose positron emission tomography (PET) have been associated with a significant risk of malignancy (8–64%). Gallium-68 (Ga-68) labelled peptides are now the standard imaging modality for staging neuroendocrine tumours (NET). Its high sensitivity has increased the discovery of incidental findings. The aim of this study was to evaluate the frequency and clinical significance of incidental thyroid uptake as detected by 68Ga- DOTANOC PET in patients without a history of thyroid cancer.

Methods: A retrospective analysis was conducted over 49 patients who underwent 68Ga-DOTANOC PET as part of a work-up for non-thyroid cancer. The uptake in the thyroid gland (focal/physiologic) was evaluated and compared with the uptake in the liver.

Results: 24 (49%) of the 49 patients were female with a median age of 64 years (p25 53 and p75 74). Thyroid nodules were known in 14 patients with a median size of 9.1±8.4 mm. The reasons for 68Ga-DOTANOC PET staging were: intestinal NET in 29 (59.2%), bronchial NET in 10 (20.4%), pancreatic NET in 5 (10.2%), paraganglioma in 2 (4.1%), an ectopic ACTH in one (2%), ectopic GH in 1 (2%) and meningioma in 1 (2%). Eight patients (16%) had 68Ga-DOTANOC thyroid uptake: one (2%) had anomalous focal uptake, and 7 (14%) had physiologic uptake. The patient with focal uptake, had thyroid nodules on the corresponding side, as detected by anatomic imaging with a final diagnosis of a benign nodule. Of the seven patients with physiologic uptake, 3 (47%) had a corresponding nodule on ultrasonography and 1 (14%) had a papillary thyroid carcinoma. Ten patients with known nodules did not have 68Ga-DOTANOC uptake, including a follicular tumour.

Conclusions: In contrast to the published research of 68Ga-DOTANOC uptake in patients with known thyroid cancer, in our short series, the incidental uptake in thyroid gland does not seem to be related.