The value of 18 F-DOPA PET/CT in patients with medullary thyroid carcinoma and increased calcitonin values Anja T. Golubić a , Eva Pasini Nemir a , Marijan Žuvić a , Andrea Mutvar a,b , Sanja Kusačić Kuna a,b , Marija Despot a , Tatjana Samardžić a and Dražen Huić a,b Aim The aim of this prospective observational study was to examine the benefit of a fluorine-18- L-dihydroxyphenylalanine ( 18 F-DOPA) PET/computed tomography (CT) scan in patients with medullary thyroid carcinoma (MTC) in terms of increased calcitonin levels. Patients and methods Twenty-eight MTC patients after initial total thyreoidectomy with increasing follow-up calcitonin levels suggestive for active disease after negative conventional imaging findings (neck ultrasound or thorax, abdomen, pelvis multislice computed tomography as standard imaging) were scanned using 18 F-DOPA PET/CT from November 2012 to April 2016. The mean calcitonin level was 108.5 (range: 6.7–290) pmol/l and the mean carcinoembryonic antigen level was 15.7 (range: 1.1–221.9) μg/l. The mean follow-up period was 19.7 months. Results 18 F-DOPA PET/CT was positive in 16 out of 28 (57%) patients, mostly because of metabolically active neck and mediastinal lymph nodes metastases. Previously unknown bone metastases were found in six patients. A positive scan was reported in four patients (25% of positive scans) with a very low calcitonin value of less than 49.9 pmol/l. PET/CT findings led to a change of management and therapy in 16 out of 28 patients, with surgical procedure performed in eight patients, radiotherapy in five patients, and chemotherapy in two patients. Conclusion 18 F-DOPA PET/CT is a clinically useful modality in MTC whenever the calcitonin level is increased. There is a clear trend toward more positive scans with the higher calcitonin values, but patients with moderately elevated calcitonin values should also be taken into consideration for molecular imaging with 18 F-DOPA PET/CT as the tumor burden in these patients is probably low, enabling further therapy to be individualized and consequently more efficient. Nucl Med Commun 38:636–641 Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. Nuclear Medicine Communications 2017, 38:636–641 Keywords: calcitonin, 18 F-DOPA, medullary thyroid carcinoma, neuroendocrine tumors, PET/CT a Department of Nuclear Medicine and Radiation Protection, University Hospital Centre Zagreb and b School of Medicine, University of Zagreb, Zagreb, Croatia Correspondence to Dražen Huić, MD, PhD, Department of Nuclear Medicine and Radiation Protection, University Hospital Centre Zagreb, Kišpatićeva 12, 10 000 Zagreb, Croatia Tel: + 385 1238 8587; fax: + 385 1237 6040; e-mail: dhuic@kbc-zagreb.hr Received 6 February 2017 Revised 4 April 2017 Accepted 4 May 2017 Introduction Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor originating from the neural crest and derived from parafollicular C cells in the thyroid gland that regulate calcium metabolism by secreting the hormone calcitonin. MTC accounts for 5% of all thyroid cancers, and although it is predominantly sporadic, in ∼ 30% of patients, it is related to RET proto-oncogene mutation, commonly in the multiple endocrine neoplasia (MEN) syndrome [1,2]. After total thyroidectomy and lymph node dissection, which is still the only curative treatment, patients should be monitored for increasing calcitonin levels and assessed for local recurrences and distant metastases. The recur- rence rate of MTC is high, up to 50%, and conventional imaging, that is, ultrasound (US), multislice computed tomography (CT), and MRI, commonly used in patient follow-up, often reports negative or equivocal findings in patients with increasing calcitonin levels [3]. Several biomarkers have been proposed for determining prog- nosis, detecting recurrence as well as predicting therapy response [4]. Functional imaging has been introduced and fluorine-18- L-dihydroxyphenylalanine ( 18 F-DOPA) PET/CT has been found to be a sensitive imaging method in the detection of locoregional and distant MTC metastases [5–8]. 18 F-DOPA is a neutral amino acid, analogous to natural L-dopa (dopamine precursor). It is taken up by a large amino acid transporter, overexpressed in neuroendocrine tumors, and decarboxylated with aromatic amino acid decarboxylase, upregulated in neuroendocrine tumors [9]. 18 F-DOPA PET/CT detection rate increases with the level of serum calcitonin and a cut-off value should be proposed [7,10]. The aim of this study is to evaluate the detection rate of 18 F-DOPA PET/CT in terms of calcitonin and carcinoembryonic antigen (CEA) levels in MTC with a focus on patient management change. Patients and methods Design and setting This prospective observational study was carried out at the Department of Nuclear Medicine and Radiation Original article 0143-3636 Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/MNM.0000000000000696 Copyright r 2017 Wolters Kluwer Health, Inc. All rights reserved.