¹³¹I whole-body scintigraphy (WBS) is a highly sensitive method for the detection of differentiated thyroid tumors and metastases. However, a lack of anatomic landmarks and the physiologic accumulation of the tracer complicate interpretation of the images. This prospective study was designed to evaluate the incremental value of ¹³¹I SPECT/CT over planar WBS in the management of patients with differentiated thyroid carcinoma (DTC). Methods: Planar imaging was performed on 66 consecutive DTC patients who were considered to have locally advanced or metastatic disease after total or nearly total thyroidectomy. SPECT/CT was added for patients whose planar findings were inconclusive. The planar images were interpreted by 2 experienced nuclear medicine physicians. Interpretation of the SPECT/CT images was a consensus opinion of one of the nuclear medicine physicians and an experienced radiologist. Fusion images were considered to improve image interpretation when they better localized sites of increased ¹³¹I uptake. The final diagnosis was verified by pathologic findings, other imaging modalities, and clinical follow-up. Both site-based and patient-based analyses were performed, and the impact of SPECT/CT results on therapeutic strategy was assessed. Results: A total of 232 foci were observed by ¹³¹I WBS, including 33.2% of foci localized in the thyroid bed, 62.1% due to malignant lesions, and 4.7% caused by nonthyroidal physiologic or benign uptake or a contaminant. Overall, 37 SPECT/CT studies were performed on 23 patients, whose planar images showed 81 inconclusive lesions. Precise localization and characterization of ¹³¹I-avid foci were achieved through ¹³¹I SPECT/CT in 69 (85.2%) and 67 (82.7%) of the 81 foci, respectively. Fusion images were considered to be of benefit in 17 (73.9%) of 23 patients. The therapeutic strategy was changed in 8 (47.1%) of 17 patients. Uncommon metastatic lesions were found in 9 (13.6%) of 66 patients with regard to SPECT/CT fusion images. Conclusion: Fusion of SPECT and CT images was of incremental value over WBS in increasing diagnostic accuracy, reducing pitfalls, and modifying therapeutic strategies in 73.9% of DTC patients. As SPECT/CT techniques emerge, ¹³¹I SPECT/CT may demonstrate higher value than WBS in the management of DTC.

Differentiated thyroid cancer (DTC) is usually indolent with good prognosis and long-term survival. However, DTC distant metastasis is often a grave event and accounts for most of its disease-specific mortality. The major sites of distant metastases are the lung and bone. Metastases to the brain, breast, liver, kidney, muscle, and skin are rare or relatively rare. Nevertheless, recognizing rare metastases from DTC has a significant impact on the clinical decision making and prognosis of patients. ¹³¹I single photon emission computed tomography/computed tomography (¹³¹I-SPECT/CT) can provide both metabolic and anatomic information about a lesion; therefore, it can better localize and define the ¹³¹I-WBS findings in DTC patients. In this pictorial review, the imaging features of a range of rare metastases from DTC are demonstrated, with a particular emphasis on the ¹³¹I-SPECT/CT diagnostic aspect.

Context: Data from a large cohort of patients with pulmonary metastases from differentiated thyroid cancer (DTC) were retrospectively analyzed.Objective: To assess the effect of radioiodine therapy and investigate the prognostic factors of survival for patients with pulmonary metastasis secondary to DTC.Methods: A total of 372 patients with pulmonary metastasis from DTC treated with¹³¹I entered the study. According to the results of¹³¹I whole-body scan (WBS), pulmonary metastases were classified as¹³¹I-avid and non-¹³¹I-avid. For patients with¹³¹I-avid lung metastases, treatment response was measured by three parameters: serum thyroglobulin (Tg) levels, chest computed tomography (CT) and post-therapeutic¹³¹I-WBS. Overall survival was calculated by the Kaplan–Meier method. Factors predictive of the outcome were determined by multivariate analyses.Results: Among patients demonstrating¹³¹I-avid pulmonary metastases (256/372, 68.8%), 156 cases (156/256, 60.9%) showed a significant decrease in serum Tg levels after¹³¹I therapy and 138 cases (138/229, 60.3%) showed a reduction in pulmonary metastases on follow-up CT. A complete cure, however, was only achieved in 62 cases (62/256, 24.2%). Multivariate analysis showed that only age, the presence of multiple distant metastases and pulmonary metastatic node size were significant independent variables between the groups of¹³¹I-avid and non-¹³¹I-avid.Conclusion: This study indicated that, most¹³¹I-avid pulmonary metastases from DTC can obtain partial or complete remission after¹³¹I therapy. Younger patients (<40 years old) with only pulmonary metastases and small (‘fine miliaric’ or micronodular) metastases appear to have relative favorite outcomes. Patients who do not respond to¹³¹I treatment have a worse prognosis.

Our objective was to investigate the clinical efficacy of (131)I therapy for bone metastases from differentiated thyroid cancer (DTC) and prognostic factors as well as to assess patient survival and variables influencing survival. One hundred six DTC patients with bone metastases treated with (131)I were retrospectively analyzed. The therapeutic efficacy was evaluated based on the change in serum thyroglobulin (Tg), the palliation of bone pain, and the anatomical imaging changes in bone lesions. The overall survival rates were estimated using the life-table method. After (131)I therapy, a significant decrease in serum Tg was seen in 37 cases (34.9%), and serum Tg remained stable in 56 patients (52.8%). Among the 61 patients with painful bone metastases, 39 patients obtained a significant relief of bone pain, and the effective rate was 63.9%. The majority of DTC patients (76.4%) exhibited no obvious anatomical imaging changes in metastatic bone lesions after (131)I therapy. Only histopathological type and whether combined with nonosseous distant metastases had statistically significant impacts on changes in serum Tg (P = 0.009 and 0.023), and age over 45 yr and papillary thyroid carcinoma had favorable response on changes in anatomical imaging (P = 0.027 and 0.014). The 5- and 10-yr survival rates were 86.5 and 57.9%, respectively. Multivariate analyses showed that the presence of solitary bone metastases, only bone metastases, and (131)I therapy with previous bone surgery were independent factors associated with a better prognosis (P = 0.024, 0.009, and 0.031). (131)I therapy is a feasible and effective treatment for DTC bone metastases. A better prognosis can be accomplished in patients who had a single metastatic lesion, only bone metastasis, or underwent bone surgery before (131)I therapy.