Clinical applications of single-photon emission computed tomography/computed tomography in post-ablation 131iodine scintigraphy in children and young adults with differentiated thyroid carcinoma

Determining the Minimum Number of Examined Lymph Nodes for N1b Papillary Thyroid Cancer Patients

BACKGROUND

This study aimed to evaluate the correlation between the number of examined lymph nodes (eLNs) and postoperative residual lateral LN disease in patients with papillary thyroid cancer (PTC) and lateral nodal metastasis (N1b) and determine the minimal threshold for the eLNs.

METHODS

Patients diagnosed with unilateral N1b PTC who underwent total thyroidectomy with therapeutic LN dissection of the central and lateral compartments between January 2012 and December 2022 were included. Multivariate logistic regression analyses were performed to identify the threshold number of eLNs that independently influenced the risk of residual lateral LN disease.

RESULTS

Residual lateral LN disease was identified in 56 (5.4%) of 1042 T1-2 patients and 74 (12.3%) of 602 T3-4 patients. When analyzed as a continuous variable, the number of eLNs in the lateral neck was independently associated with a reduced risk of residual lateral LN disease in both T1-2 (OR: 0.93; 95% CI: 0.90-0.97; p < 0.001) and T3-4 patients (OR: 0.94; 95% CI: 0.91-0.97; p < 0.001). As a categorical variable, the risk of residual lateral LN disease continued to decrease significantly until the number of eLNs reached 34 in T1-2 patients and 46 in T3-4 patients.

CONCLUSION

Comprehensive preoperative imaging for LN status and systematic compartmental dissection of the affected levels are critical in managing N1b PTC. To minimize the risk of residual lateral LN disease, the minimum recommended number of eLNs in the lateral neck is 34 for T1-2 patients and 46 for T3-4 patients.

LEVEL OF EVIDENCE

4-retrospective cohort study.

Whole-body effective half-life of radioiodine in children and young adults with papillary thyroid cancer

PURPOSE

The lack of radioiodine-131 (RAI) kinetic study is a serious challenge for rational dosing for children and young adults (CYAs) with papillary thyroid cancer (PTC). The present study was conducted to investigate the whole-body effective half-life (EHL) and absorbed dose in RAI ablative therapy of CYAs with PTC.

METHODS

In the period 2017-2022, all consecutive PTC patients 20 years or younger prepared for ablative RAI therapy after thyroid hormone withdrawal were prospectively recruited. Serial whole-body dose-rate measurements after administration were performed to deduce whole-body RAI retention. Calculations based on the deduced whole-body retention and the schema of Medical Internal Radiation Dosimetry were derived to determine whole-body EHL and absorbed doses. A multivariate linear regression analysis was employed to assess the association between whole-body EHL and potential predictors.

RESULTS

A total of 52 patients (median age 17 years [range, 6-20 years]) were recruited. The mean whole-body EHL (±SD) was 10.3 (3.3) hours (median, 9.4 h [range, 6.3-21.7 h]). In univariable linear regression analysis, whole-body EHL was significantly associated with gender, body surface area (BSA) and body mass index (p < 0.05). Creatinine, Cystatin C, glomerular filtration rate (GFR) and positive post-ablation scintigraphy approached significance with respect to EHL (p ≤ 0.2 and ≥0.05). At multivariable analysis, BSA, GFR and positive post-ablation scintigraphy was associated with EHL. A median activity of 3.7 GBq of RAI (range, 1.85-7.40 GBq) was administered and a median whole-body absorbed dose of 0.22 Gy was delivered (range, 0.11-0.79 Gy).

CONCLUSION

A wide variation of whole-body EHL was observed in CYAs with PTC treated with RAI. The whole-body EHL is significantly longer in CYAs with larger BSA, decreased GFR and presence of extra-thyroidal disease. Understanding these predictors may improve our ability to dosing strategies in RAI therapy of CYAs with PTC.

Current Advances in Radioactive Iodine-Refractory Differentiated Thyroid Cancer

BACKGROUND

Differentiated thyroid cancer (DTC) patients have an outstanding overall long-term survival rate, and certain subsets of DTC patients have a very high likelihood of disease recurrence. Radioactive iodine (RAI) therapy is a cornerstone in DTC management, but cancer cells can eventually develop resistance to RAI. Radioactive iodine-refractory DTC (RAIR-DTC) is a condition defined by ATA 2015 guidelines when DTC cannot concentrate RAI ab initio or loses RAI uptake ability after the initial therapy. The RAIR condition implies that RAI cannot reveal new met-astatic foci, so RAIR-DTC metabolic imaging needs new tracers. 18F-FDG PET/CT has been widely used and has demonstrated prognostic value, but 18F-FDG DTC avidity may remain low. Fibroblast activation protein inhibitors (FA-Pi)s, prostatic-specific membrane antigen (PSMA), and somatostatin receptor (SSTR) tracers have been proposed as theragnostic agents in experimental settings and Arg-Gly-Asp (RGD) peptides in the diagnostic trial field. Multi-targeted tyrosine kinase inhibitors are relatively new drugs approved in RAIR-DTC therapy. Despite the promising targeted setting, they relate to frequent adverse-event onset. Sorafenib and trametinib have been included in re-differentiation protocols aimed at re-inducing RAI accumulation in DTC cells. Results appear promising, but not excellent.

CONCLUSIONS

RAIR-DTC remains a challenging nosological entity. There are still controversies on RAIR-DTC definition and post-RAI therapy evaluation, with post-therapy whole-body scan (PT-WBS) the only validated criterion of response. The recent introduction of multiple diagnostic and therapeutic agents obliges physicians to pursue a multidisciplinary approach aiming to correct drug introduction and timing choice.

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.

False-Positive Radioactive Iodine Uptake Caused by Cervical Myofascitis in a Patient With Differentiated Thyroid Carcinoma

ABSTRACT

A 31-year-old woman with a history of papillary thyroid cancer underwent ablative 131I therapy. Posttherapeutic whole-body 131I scintigraphy revealed abnormally increased activity in the neck. Additional SPECT/CT images localized the activity in the bilateral peripheral fascia of the platysma.

Paediatric differentiated thyroid carcinoma: a UK National Clinical Practice Consensus Guideline

This guideline is written as a reference document for clinicians presented with the challenge of managing paediatric patients with differentiated thyroid carcinoma up to the age of 19 years. Care of paediatric patients with differentiated thyroid carcinoma differs in key aspects from that of adults, and there have been several recent developments in the care pathways for this condition; this guideline has sought to identify and attend to these areas. It addresses the presentation, clinical assessment, diagnosis, management (both surgical and medical), genetic counselling, follow-up and prognosis of affected patients. The guideline development group formed of a multi-disciplinary panel of sub-speciality experts carried out a systematic primary literature review and Delphi Consensus exercise. The guideline was developed in accordance with The Appraisal of Guidelines Research and Evaluation Instrument II criteria, with input from stakeholders including charities and patient groups. Based on scientific evidence and expert opinion, 58 recommendations have been collected to produce a clear, pragmatic set of management guidelines. It is intended as an evidence base for future optimal management and to improve the quality of clinical care of paediatric patients with differentiated thyroid carcinoma.

An Unusual False-Positive Uptake of Radioiodine Caused by Posttraumatic Superficial Scab

ABSTRACT

A 22-year-old man with a history of recurrent papillary thyroid cancer underwent 131I therapy. Posttherapeutic whole-body scintigraphy was performed 5 days after administration of 5.5 GBq of 131I. The scintigraphy revealed increased activity in the left elbow. On physical examination, the patient had posttraumatic superficial scab at the site of the abnormal activity.

An Unusual False-Positive Uptake of Radioiodine Caused by Breast Implants

ABSTRACT

A 40-year-old woman with a history of papillary thyroid cancer underwent ablative 131I therapy. Postablation whole-body 131I scintigraphy revealed not only increased activity in the thyroid bed but also in the anterior part of the chest. SPECT/CT images localized the activity in the bilateral breast implants.

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.