Medullary Thyroid Carcinoma: Do Ultrasonography and F-DOPA-PET-CT Influence the Initial Surgical Strategy?

Abstract

BackgroundAt the time of diagnosis, one-third of medullary thyroid carcinoma (MTC) patients show lymph node (LN) or distant metastasis. A metastasized MTC requires different surgical strategies.ObjectiveThis study aimed to determine the value of ultrasound and [18F]fluoro-dihydroxyphenylalanine positron emission tomography with computed tomography (F-DOPA-PET-CT) in localizing MTC, as well as LN and distant metastasis.MethodsThe study included 50 patients (24 males/26 females) with preoperative ultrasound, F-DOPA-PET-CT, and histologically proven MTC. Imaging results were correlated with both preoperative basal calcitonin (bCt) levels and final histology.ResultsTumors were classified as pT1a:17 (diameter, mean ± standard deviation: 5.8 ± 3.0 mm), pT1b:15 (15.0 ± 3.2 mm), pT2:9 (27.3 ± 7.0 mm), and pT3:9 (38.3 ± 24.2 mm). The median bCt level was 202 pg/mL (lower/upper quartile: 82/1074 pg/mL). Ultrasound was positive for tumor in 45/50 (92%) patients (20.0 ± 16.0 mm) and negative in 5 patients (3.2 ± 2.2 mm). Overall, 43/50 (86%) patients had positive F-DOPA local scans (20.0 ± 16.4 mm), while 7 (14%) patients were negative (7.7 ± 8.1 mm). Lastly, 21/50 (42%) patients had LN metastasis; 8/21 (38%) patients had positive LNs suspected with ultrasound, and 12/21 (57%) patients had positive LNs suspected with F-DOPA. Tumor and LN sensitivity of ultrasound was 92% and 43%, respectively, and 86% and 57% of F-DOPA-PET-CT, respectively. In 3/50 (6%) patients and 3/50 (6%) patients, mediastinal LN metastasis and distant metastasis, respectively, were diagnosed only by F-DOPA-PET-CT.ConclusionUltrasound and F-DOPA-PET-CT are sensitive for the localization of MTC but not for the presence and location of LN metastasis (limitations: size/number). Only F-DOPA ensures the diagnosis of distant metastasis and influences the extent of LN surgery. Surgical strategy cannot be predicted based on neither ultrasound nor F-DOPA-PET-CT.

Medullary thyroid carcinoma: recent advances in identification, treatment, and prognosis

“… 36 – 38 The utility of detecting MTC with 18 F-DOPA PET/CT increases proportionally to increases in basal calcitonin in the context of both initial and recurrent disease. 39 , 40 One study evaluating the utility of F-DOPA PET/CT in patients with persistent or recurrent disease found the sensitivity of the study was markedly improved with a serum calcitonin level greater than 150 pg/mL (sensitivity 91% versus 29%) as the cutoff for imaging for metastatic disease according to 2015 ATA guidelines. 3 , 38 …”

Diagnostic Challenges of Medullary Thyroid Carcinoma

“…In a review of 50 patients with elevated serum Ctn, thyroid ultrasound positively identified 90% of patients with malignant nodules compared to F-DOPA-PET-CT imaging correctly identifying 86%, with 14% labeled as false negative. However, F-DOPA-PET-CT imaging correctly identified all patients with distant metastasis [54]. Other reports showed much more limited sensitivity, with a 66% detection rate on a per-patient basis and a 71% detection rate on a perlesion basis in a review of 139 patients with known MTC [59].…”

“…1). Thyroid ultrasound has a reported sensitivity of 90% in identifying a malignant lesion in the correct thyroid lobe, but only 71% sensitivity in localizing microcarcinoma [54]. In a study of 118 patients with MTC, approximately 86% were in middle or upper poles [55].…”

Endokrine und neuroendokrine Tumoren

“…Beim MTC steht mit dem ( 18 F-)DOPA-PET/CT auch eine molekulare Bildgebung zur Verfügung, die bei fortgeschrittener Erkrankung hilfreich sein kann [ 2 ].…”