Can (18)F-FDG-PET/CT be generally recommended in patients with differentiated thyroid carcinoma and elevated thyroglobulin levels but negative I-131 whole body scan?
ABSTRACT Exact localization of recurrent iodine-negative thyroid cancer is mandatory, since surgery is the only curative therapy option in patients with iodine-negative tumor tissue. The aim of this study was to evaluate the impact of (18)F-FDG-PET/CT as a routine diagnostic tool on clinical management in patients with suspected thyroid cancer recurrence and elevated serum thyroglobulin (Tg) but negative radioiodine whole body scan.
After total thyroidectomy followed by radioiodine ablation, 30 consecutive patients with differentiated thyroid cancer, elevated serum thyroglobulin levels and negative whole body radioiodine scan underwent (18)F-FDG-PET/CT. Results were verified by histology, ultrasound, or clinical follow-up. Diagnostic accuracy was determined for the whole study population and for subgroups with serum thyroglobulin below and above 10 ng/ml, respectively. Impact of PET/CT on clinical management was assessed.
PET/CT identified FDG accumulating lesions in 19 of 30 patients. 17 were true-positive and 2 false-positive. In the true-positive group, 11 of the 17 patients had loco-regional disease, 3 had distant metastases only and 3 patients had both loco-regional and distant metastatic involvement. (18)F-FDG-PET/CT was true-negative in 3 patients and false-negative in 8 patients. Overall sensitivity, specificity and accuracy were 68.0, 60.0, and 66.7%, respectively. In the subgroup of patients with serum thyroglobulin above 10 ng/ml (n = 21) the sensitivity, specificity and accuracy were substantially higher with 70.0, 100.0, and 71.4%, respectively. Clinical management was changed for 17 (57%) of 30 patients, guiding to a curative surgical intervention in 9 patients (30%).
(18)F-FDG-PET/CT enables detection and precise localization of loco-regional recurrence and distant metastases of differentiated thyroid cancer in patients with elevated serum thyroglobulin but negative radioiodine with significant impact on patient management and can therefore be recommended as a routine diagnostic tool.
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ABSTRACT: (18)F-fluorodeoxyglucose-positron emission tomography/computed tomography (PET/CT) has proved effective in detecting recurrent or metastatic differentiated thyroid carcinoma (DTC) in the follow-up of operated DTC patients with high thyroglobulin (Tg) levels and negative findings on radioiodine whole-body scan. The aim of this retrospective study was to assess the impact of PET/CT on the planning of appropriate treatment for known recurrent disease in operated DTC patients. The study concerned 44 consecutive DTC patients (36 papillary, 8 follicular), who underwent total thyroidectomy and thyroid remnant ablation with (131)I and PET/CT. All patients had proven or strongly suspected recurrent disease judging from neck ultrasound (US) and fine-needle aspiration cytology, and detectable basal Tg levels. PET/CT findings were positive in 25/44 patients (56.81 %) and negative in 19. A positive PET/CT result predicted resectable tumour recurrences in 19/25 patients, but also detected additional tumour sites that prompted changes to the treatment plan in 6/25 patients (24 %). A negative PET/CT result led to clinical monitoring for 11/19 patients (57.89 %). PET/CT can help select patients, who might benefit from a tailored therapy by improving the detection of local recurrences not apparent on neck US or metastases.La radiologia medica 11/2013; · 1.46 Impact Factor
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ABSTRACT: Background: The expression of somatostatin receptors (SSTR) in thyroid cells may offer the possibility to identify metastatic lesions and to select patients for peptide receptor radionuclide therapy (PRRT). We investigated 68Ga-DOTATOC positron emission tomography/computed tomography (PET/CT) to select patients with progressive differentiated thyroid cancer (DTC) for PRRT as well as treatment response and toxicity in treated patients. Methods: we enrolled 41 patients with progressive radioiodine negative DTC (24 women and 17 men, mean age=54.3, median 59, range 19-78 years). In all patients [18F]FDG-PET/CT was performed to determine recurrent disease with enhanced glucose metabolism. 68Ga-DOTATOC PET/CT was used to identify SSTR expression. Dosimetric evaluation was performed with 111In-DOTATOC scintigraphy. Eleven patients were treated with PRRT receiving fractionated injection of 1.5-3.7 GBq 90Y-DOTATOC/administration. Serial 68Ga-DOTATOC PET/CT scans were performed in all treated patients to evaluate treatment response. Parameters provided by 68Ga-DOTATOC PET/CT were analyzed as potential therapeutic predictors to differentiate responding from non-responding. In all treated patients adverse events and toxicity were recorded. Results: 68Ga-DOTATOC PET/CT resulted positive in 24/41 of radioiodine negative DTC patients. Based on the high expressions of SSTR detected by 68Ga-DOTATOC PET/CT 13 patients were suitable for PRRT. Two out of 13 were not treated due to the lack of fulfilment of other study inclusion criteria. PRRT induced disease control in 7/11 patients (2 partial response and 5 stabilization) with a duration of response of 3.5-11.5 months. Objective response was associated with symptoms relief. Functional Volume (FV) over time obtained by PET/CT was the only parameter demonstrating a significant difference between lesions responding and non-responding to PRRT (p=0.001). Main PRRT adverse events were nausea, astenia and transient hematologic toxicity. One patient experienced permanent renal toxicity. Conclusions: In our series, SSTR imaging provided positive results in more than half of the cases with radioiodine negative DTC and admitted to PRRT about one third of patients. 68Ga-DOTATOC PET/CT seems a reliable tool both for patient selection and evaluation of treatment response. In our experience, FV determination over time seems to represent a reliable parameter to determine tumor response to PRRT, although further investigations are needed to better define its role.Thyroid: official journal of the American Thyroid Association 10/2013; · 2.60 Impact Factor
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ABSTRACT: The aim of the study was to disclose the place of (18)F-FDG PET/CT to predict recurrent disease in patients with differentiated thyroid cancer (DTC), negative radioiodine whole-body scan (WBS) and high serum thyroglobulin (Tg). Seventy-one patients who underwent total thyroidectomy followed by radioactive iodine ablation and had negative radioiodine WBS but elevated Tg levels underwent PET/CT. They were followed up for 6-50 months (median 23) for the occurence of recurrent disease as detected by either clinical findings, other imaging modalities or histopathological examination. The place of PET/CT findings at baseline to predict the presence of recurrent disease was evaluated. Correlation between PET/CT findings and Tg levels was examined and a threshold for Tg level above which the predictive value of PET/CT was highest was determined. PET/CT was positive for recurrent disease in 38 (53.5 %) patients. The sensitivity, specificity, PPV, NPV and diagnostic accuracy of PET/CT to predict the occurence of recurrent disease at follow-up were 68.8, 78.3, 86.8, 54.5 and 71.9 %, respectively. The sensitivity, accuracy and PPV of PET/CT increased with increasing Tg levels. The highest diagnostic accuracy of PET/CT, with a sensitivity of 76.2 % and a specificity of 100 % to detect recurrent disease appeared to be at a Tg level greater than 29 ng/mL. Our findings suggest that (18)F-FDG-PET/CT is a valuable tool to predict the occurence of recurrent disease in patients with DTC, negative WBS and elevated Tg levels. PET/CT positivity has been shown to be strongly and positively correlated with Tg levels in this patient subset.Annals of Nuclear Medicine 12/2013; · 1.41 Impact Factor