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: Background: Management of patients with thyroglobulin (Tg)-positive/scan-negative thyroid cancer remains challenging. American Thyroid Association (ATA) guidelines recommend potential use of empiric I-131 therapy and various scanning modalities, but no standard for managing such cases exists. Methods: We surveyed ATA members to assess current practice in management of patients with Tg-positive/scan-negative disease. Members participated in a web-based survey of six case scenarios of Tg elevations but iodine scan negativity. Results: A total of 288 ATA members (80% male) participated. Patient age, sex, and basal and stimulated Tg varied between the cases. Respondents were asked their opinion regarding empiric I-131 therapy use, including I-131 dose, use and duration of low-iodine diet, thyroxine withdrawal or recombinant human thyrotropin (rhTSH), and utilization of additional imaging (neck ultrasound (US) or positron emission tomography/computed tomography (PET/CT)) and reconsideration of I-131 therapy. Between 16% and 51% recommended initial use of empiric I-131 for the various scenarios. The majority chose a I-131 dose between 75 and 150 mCi, and 73% employed a low-iodine diet for two or more weeks. Preference between thyroxine withdrawal versus rhTSH was evenly split. More than 98% obtained a neck US if empiric I-131 was not given; 52-89% would proceed to PET/CT if US was negative. Only 44% used rhTSH stimulation in PET scan preparation. I-131 use was more common with stimulated Tg significantly >10 ng/mL. I-131 therapy was slightly more likely with PET-positive (56%) than PET-negative status (45%). Respondents were split regarding empiric I-131 if basal and stimulated Tg increased >= 150% over two years. Providers in North America less commonly utilized I-131 treatment than those from other areas. In the face of possible heterophilic antibody interference in the Tg assay, the majority did not recommend I-131 therapy. Conclusions: Empiric I-131 therapy is still utilized for patients with Tg-positive/scan-negative disease. Neck US is frequently used to further evaluate such cases as (18)FDG-PET/CT, albeit the latter is used somewhat less often. Use of I-131 therapy correlated with the degree of Tg elevation or development of Tg antibodies, and was recommended more commonly with PET-positive than PET-negative status in patients with lower Tg levels. I-131 was less commonly used by providers within North America.Thyroid: official journal of the American Thyroid Association 07/2014; 24(10). DOI:10.1089/thy.2014.0043 · 3.84 Impact Factor
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ABSTRACT: Background: Rebound thymic hyperplasia (RTH) is not an uncommon finding after radiation or chemotherapy in patients with various malignancies. However, there are limited case reports of this phenomenon after radioactive iodine ablation therapy (RIAT) in differentiated thyroid cancer (DTC). The goal of this study was to evaluate the incidence, patterns, and affecting factors of RTH after RIAT by using 18F-FDG PET/CT. Methods: The study design was a retrospective review of 2550 patients (568 men, 1982 women; age, 13-79 years) who underwent FDG PET/CT imaging after total thyroidectomy and RIAT from June 2009 through June 2012. Patients were divided into 4 age-related subgroups. Overall incidence, age-related incidences, and gender distribution were evaluated in patients with thymic FDG uptake on PET/CT (RTH+). The correlation between incidence of RTH and age was assessed using the Cochran-Armitage trend test, and the Wilcoxon rank-sum test and multiple regression were applied to investigate the effect of applied dose of radioactive iodine (RAI) and age on the incidence of RTH. Correlations of standardized uptake value (SUV) and thymic volume with age and morphologic type were also evaluated. Results: Overall incidence of RTH after RIAT was 1.49%, and all of the RTH+ patients except one were female. The Cochran-Armitage trend test revealed significantly decreased incidence from the second to fifth decade (8.84%, 1.74%, 0.98%, and 0.39%, respectively; P < 0.001). In each age-related subgroup, the RAI dose was significantly higher in the RTH+ than RTH- group (P < 0.001), while there was no difference in RAI dose in RTH+ patients among age-related subgroups (P = 0.838). SUVmean and SUVmax of RTH revealed no meaningful correlation with RAI dose or age. There were no differences among morphologic patterns of RTH in age distribution and ablation dose. Conclusions: RTH after RIAT showed a strong female predominance despite the higher administration dose of RAI in male patients. Although the decreased incidence of RTH after RIAT with age is similar to the pattern of RTH induced by other causes, the fact that older patients, even sixth decade patients, can present with RTH after RIAT is noteworthy in the management of DTC.Thyroid: official journal of the American Thyroid Association 07/2014; 24(11). DOI:10.1089/thy.2014.0164 · 3.84 Impact Factor
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ABSTRACT: Technology and IT are major developments over the past 30 years. Advances in nuclear medicine imaging allow a more personalized patient therapeutic management based on the metabolic mapping established with radioiodine scintigraphy and/or FDG-PET. Thus, this physiological imaging is closely related to therapy. Meanwhile PET with iodine 124, we still get a lot of information with iodine 131 scintigraphy performed during iodine therapy, despite a poor spatial resolution. Hybrid imaging coupling tomoscintigraphy and CT (SPECT/CT) reveals significant hidden or unexplained on planar acquisitions information. PET/CT with FDG or iodine 124 may help in the diagnosis of disease recurrence. But it is for aggressive or metastatic disease that the iodine-FDG mapping becomes mandatory. FDG is the crystal ball that writes the future of metastatic disease. Iodine 131 will have its efficiency reduced and patient survival flexed as much as FDG uptake increases. As disease becomes iodine refractory, it will be referred to targeted therapies with many side effects. We look forward to get the selumetinib, a tyrosine kinase inhibitor, which makes reappeared iodine uptake and thus replaces iodine 131 at the forefront of the therapeutic arsenal.Medecine Nucleaire 05/2014; DOI:10.1016/j.mednuc.2014.03.004 · 0.16 Impact Factor