I-131 Postablation SPECT/CT Predicts Relapse of Papillary Thyroid Carcinoma more Accurately than Whole Body Scan

Current and Emerging Radiotracers and Technologies for Detection of Advanced Differentiated Thyroid Cancer: A Narrative Review

Differentiated thyroid cancer (DTC), which includes papillary and follicular thyroid cancers, differs significantly in pathology compared to other thyroid malignancies such as medullary thyroid cancer (MTC), anaplastic thyroid cancer (ATC), and Hurthle cell carcinoma [...].

Pre-Treatment and Post-Treatment I-131 Imaging in Differentiated Thyroid Carcinoma

Radioiodine imaging in initial perioperative settings, after the total thyroidectomy, includes pre-treatment and post-treatment radioiodine imaging. While the benefit of post-treatment whole-body imaging (PT-WBI) is well established, the role of diagnostic whole-body imaging (dx WBI), prior to radioiodine (I-131) ablative or therapeutic doses, is controversial. Dx WBI has been abandoned in most nuclear medicine centers long ago. Planar low-dose dxWBI provides the volume of postoperative thyroid remnants, but it cannot detect occult metastatic foci in the neck. The modern integrated multimodality, i.e., SPECT/CT imaging, provides three dimensional images and accurate anatomic/metabolic data. This hybrid technology offers better spatial resolution but not better sensitivity. Dx WBI has low theranostic power because of the radioiodine indifference and low detection sensitivity for small-volume nodal disease in the neck. Since dx WBI cannot clarify the paratracheal cervical uptake, thyroid remnants may be easily misinterpreted as nodal disease, leading to a false N upstaging (from N0 stage to N1 stage) in DTC patients. Post-ablation I-131 imaging has a significant role in the initial staging of radioiodine-avid DTC and in the identification of non-radioiodine avid tumors. Additionally, SPECT/CT in the post-treatment setting provides more accurate initial TNM staging and better risk stratification of DTC patients. Post-treatment I-131 imaging is obligatory and must be performed in all DTC patients who receive radioiodine treatment.

Clinical Implications of Adding SPECT/CT to Radioiodine Whole-Body Scan in Patients With Differentiated Thyroid Cancer: A Systematic Review and Meta-analysis

PURPOSE

This study aimed to determine the usefulness of adding SPECT/CT to radioiodine whole-body scans (WBSs) for the treatment of differentiated thyroid cancer (DTC).

PATIENTS AND METHODS

A systematic review and meta-analysis were performed following the PRISMA guidelines (PROSPERO registration: CRD42022341732) to compare the feasibility of conclusive readings and the frequency of changes in treatment plans in patients with DTC undergoing WBS + SPECT/CT versus WBS. MEDLINE, EMBASE, and Cochrane databases were searched to identify relevant articles concerning thyroid cancer, radioactive iodine, and SPECT/CT or SPECT, published before August 16, 2023. Studies not comparing WBS + SPECT/CT with WBS, those lacking target outcomes, and those not involving human subjects were excluded. The risk of bias was assessed using the RoBANS 2.0 (Risk of Bias Assessment Tool for Nonrandomized Studies) tool. The GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) system was used to evaluate the quality of evidence and strength of recommendations.

RESULTS

A total of 30 studies (prospective n = 9, retrospective n = 21) were included in the meta-analyses. Adding SPECT/CT to WBS was shown to increase conclusive readings for cervical lesions, extracervical lesions, and all regions. Lesion-based analyses showed improvements of 14%, 20%, and 18%, respectively, whereas scan-based analyses showed improvements of 27%, 9%, and 34%. The addition of SPECT/CT to WBS led to changes in 30% of treatment plans after diagnostic scans and 9% of treatment plans after posttherapeutic scans. The quality of evidence and strength of recommendations were low.

CONCLUSIONS

Compelling evidence demonstrates that the addition of SPECT/CT to WBS improves lesion localization, diagnostic performance, and therapy plan for patients with DTC.

Clinical experience following implementation of routine SPECT-CT imaging following 131-iodine administration for thyroid cancer

Background

Planar scintigraphy has long been indicated in patients receiving I-131 therapy for thyroid cancer to determine the anatomic location of metastases. We studied our experience upon implementing additional single-photon emission (SPECT)-CT scanning in these patients.

Method

We performed a retrospective study of consecutive adult patients with newly diagnosed thyroid cancer treated with I-131 between 2011 and 2017. Radiologic findings detected with planar scintigraphy alone vs those identified with SPECT-CT scanning were primary endpoints.

Result

In this study, 212 consecutive patients with thyroid cancer were analyzed in two separate cohorts (107 planar scintigraphy alone and 105 planar scintigraphy with SPECT-CT). The addition of SPECT-CT resulted in more findings, both thyroid-related and incidental. However, we identified only 3 of 21 cases in which SPECT-CT provided an unequivocal additional benefit by changing clinical management beyond planar scintigraphy alone. No difference in the detection of distant metastatic disease or outcome was identified between cohorts.

Conclusion

Synergistic SPECT-CT imaging in addition to planar nuclear scintigraphy adds limited clinical value to thyroid cancer patients harboring a low risk of distant metastases, while frequently identifying clinically insignificant findings. These data from a typical cohort of patients receiving standard thyroid cancer care provide insight into the routine use of SPECT-CT in such patients.

Classification and Diagnosis of Residual Thyroid Tissue in SPECT Images Based on Fine-Tuning Deep Convolutional Neural Network

Patients with thyroid cancer will take a small dose of 131I after undergoing a total thyroidectomy. Single-photon emission computed tomography (SPECT) is used to diagnose whether thyroid tissue remains in the body. However, it is difficult for human eyes to observe the specificity of SPECT images in different categories, and it is difficult for doctors to accurately diagnose the residual thyroid tissue in patients based on SPECT images. At present, the research on the classification of thyroid tissue residues after thyroidectomy is still in a blank state. This paper proposes a ResNet-18 fine-tuning method based on the convolutional neural network model. First, preprocess the SPECT images to improve the image quality and remove background interference. Secondly, use the preprocessed image samples to fine-tune the pretrained ResNet-18 model to obtain better features and finally use the Softmax classifier to diagnose the residual thyroid tissue. The method has been tested on SPECT images of 446 patients collected by local hospital and compared with the widely used lightweight network SqueezeNet model and ShuffleNetV2 model. Due to the small data set, this paper conducted 10 random grouping experiments. Each experiment divided the data set into training set and test set at a ratio of 3:1. The accuracy and sensitivity rates of the model proposed in this paper are 96.69% and 94.75%, which are significantly higher than other models (p < 0.05). The specificity and precision rates are 99.6% and 99.96%, respectively, and there is no significant difference compared with other models. (p > 0.05). The area under the curve of the proposed model, SqueezeNet, and ShuffleNetv2 are 0.988 (95% CI, 0.941-1.000), 0.898 (95% CI, 0.819-0.951) (p = 0.0257), and 0.885 (95% CI, 0.803-0.941) (p = 0.0057) (p < 0.05). We prove that this thyroid tissue residue classification system can be used as a computer-aided diagnosis method to effectively improve the diagnostic accuracy of thyroid tissue residues. While more accurately diagnosing patients with residual thyroid tissue in the body, we try our best to avoid the occurrence of overtreatment, which reflects its potential clinical application value.

Appraisal of radioiodine refractory thyroid cancer: advances and challenges

The incidence of thyroid cancer ranks top among all endocrine cancers, which has increased worldwide. Some patients suffer from recurrent/residual diseases after primary treatment. The recurrent/residual disease often turns out to be radioiodine refractory and shows poor response to radioiodine therapy. A lot of studies have explored the precise appraisal of radioiodine refractory disease in recent years. The mechanism of iodine uptake and the definition of radioiodine refractory disease have been summarized and discussed. The advances in tumor characteristics, histologies, and mutant conditions have been explored for a more accurate method in the early-stage appraisal. We then offer a review of opinions in the evaluation of refractory disease during follow-up, including Tg doubling time, ¹⁸F PET/CT, ¹³¹I WBS, and others. The sensitivity and specificity have been compared between different diagnostic methods. Some novel methods may be introduced for more precise appraisal, such as a scoring system and RNA expression profiling. This review aims to provide physicians a broad insight into the appraisal of radioiodine refractory disease and to pave way for future study.