Better Yield of ¹⁸Fluorodeoxyglucose-Positron Emission Tomography in Patients with Metastatic Differentiated Thyroid Carcinoma during Thyrotropin Stimulation

Abstract

To determine whether (18)fluorodeoxyglucose-positron emission tomography (FDG-PET) for the detection of recurrences or metastases of differentiated thyroid carcinoma should be performed during thyrotropin (TSH) suppression or TSH stimulation, eight patients were studied sequentially. After the second FDG-PET scan, a therapeutic (131)I dose was administered with posttherapy scans obtained 10 days later. Both FDG-PET scans were compared with each other and with the (131)I posttherapy whole body scans by two independent observers. Findings were verified using other imaging modalities or biopsies. Median TSH was 0.04 mU/L during TSH suppression and 64 mU/L during TSH stimulation. The FDG-PET scans during TSH suppression showed abnormalities in four patients and the FDG-PET scan during TSH stimulation in five patients. One patient was only positive during TSH stimulation. In two other patients the FDG-PET scan during TSH stimulation clearly identified more lesions, and in all positive patients lesion contrast was better during TSH stimulation. In two patients FDG-PET findings during TSH stimulation led to a change in clinical management. Thus, the performance of FDG-PET during TSH stimulation was either superior or equal to FDG-PET during TSH suppression, but never inferior. To detect metastatic or recurrent differentiated thyroid carcinoma FDG-PET should be performed during hypothyroidism, leading to TSH stimulation.

Clinical utility of 18F-FDG PET/CT in the follow-up of a large cohort of patients with high-risk differentiated thyroid carcinoma

“…As a matter of fact, more important than the influence of rhTSH or thyroid hormone withdrawal in 18 F-FDG PET/CT is the presence of high levels of Tg (Tg/ TSH or Tg/LT4 > 10 ng/mL). Over the last years, it has been demonstrated that both strategies, with or without TSH stimulation, do not considerably lead to management changes (12,32). Additional factors than sTg that influence 18 F-FDG PET/CT sensitivity are tumor de-differentiation and larger tumor burden (6), as we have seen in our results.…”

The role of TSH for 18F-FDG-PET in the diagnosis of recurrence and metastases of differentiated thyroid carcinoma with elevated thyroglobulin and negative scan: a meta-analysis

“…After reading the full text of 13 potentially relevant publications, six were excluded because they were retrospective studies without controls and did not fulfill the inclusion criteria (7,(15)(16)(17)(18)(19). Seven prospective controlled clinical trials with 168 patients were included (8,9,11,(20)(21)(22)(23) …”

“…In our review, seven prospective controlled clinical trials (8,9,11,(20)(21)(22)(23) involving 168 patients were included. Because of the low incidence, prolonged clinical course, and anticipated formidable sample sizes required for DTC, which has an overall excellent prognosis, it will be difficult to design and conduct a Table 2 Characteristics of the imaging factors and quality of the included studies.…”

“…Primary outcomes PET scans under TSH stimulation (THW or rhTSH) vs THS showed statistically significant differences in the number of patients with PET truepositive lesions (seven studies (8,9,11,(20)(21)(22)(23) Secondary outcomes PET scans taken TSH stimulation (THW or rhTSH) versus THS showed statistically significant differences in the number of the PET-detected Fig. 4.…”

“…Do TSH stimulations done under THW or rhTSH before PET increase the detection of tumor sites? PET imaging done under TSH stimulation reveals more lesions in a greater number of patients with a significantly increased tumor-to-background ratio than paired scans done during TSH suppressive therapy (THS) (7)(8)(9). However, no significant scan outcomes were found in other studies (10,11).…”