Less than 2% of the Low- and Intermediate-Risk Differentiated Thyroid Cancers Show Distant Metastases at Post-Ablation Whole-Body Scan

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.

Pros and cons of an aggressive initial treatment with surgery and radioiodine treatment in minimally invasive follicular thyroid carcinoma

BACKGROUND

Currently, surgery alone is the gold standard treatment for minimally invasive follicular thyroid cancer (mi-FTC).

CASE PRESENTATION

A case of a mi-FTC diagnosed in 1994 was treated with total thyroidectomy and radioiodine (RAI) ablation, according to the therapeutic algorithm used at that time. Nevertheless, he had a recurrence with distant metastasis after 24 years from the initial treatment.

CONCLUSION

Total thyroidectomy and RAI ablation might have delayed the development of distant metastasis but they were not sufficient to avoid disease recurrence. Certainly, remnant ablation simplified the follow-up and the monitoring of serum thyroglobulin allowed the early detection of the biochemical recurrence, but didn't change the outcome of the disease. Moreover, because of this early detection the patient was exposed to useless biochemical and imaging examinations. The aim of this report is to discuss the pros and cons of an aggressive treatment of a patient with mi-FTC.

The outcome of treatment in differentiated thyroid cancer according to recommendations in current Dutch and American guidelines

OBJECTIVE

Assessment of treatment outcome in current de-escalation for differentiated thyroid cancer (DTC) according to the 2015 Dutch thyroid cancer guidelines (NL-15) and American Thyroid Association guidelines (ATA-15).

DESIGN

Retrospectively, the recommendations of the NL-15 and ATA-15 guidelines were evaluated to estimate potentially adequate, under- and overtreatment of DTC in patients treated in the University Medical Center Groningen between 2007 and 2017.

PATIENTS

A total of 240 patients with a cT1-T3aN0-1aM0 DTC fulfilled the inclusion criteria.

MEASUREMENTS

After actual treatment was given, patients were again categorized according to both guidelines into low, intermediate, or high-risk based on tumour status. Next, they were categorized into a congruent low-risk (n = 60), congruent high-risk (n = 73), or incongruent risk group (n = 107). Follow-up data were used to estimate the proportion of potentially adequate, under-, and overtreatment according to both guidelines.

RESULTS

Comparing treatment recommended by NL-15 and ATA-15 showed significantly more over- and adequate treatment when following NL-15 recommendations, and more undertreatment following ATA-15 (all: p < .001). Subanalysis of the congruent low-risk group showed overtreatment in 64% when following NL-15 guidelines (p < .001). No treatment differences were found in the congruent high-risk group. Undertreatment was most often seen in the incongruent risk group when following ATA-15 (p < .001).

CONCLUSIONS

Low-risk patients were treated too aggressively when following NL-15 recommendations, where the less aggressive ATA-15 approach seemed more adequate. Treatment of intermediate risk DTC patients varies greatly, with a relative higher rate of undertreatment according to the recommendations of the ATA-15, advocating further refining of the risk classification in this patient group.

Treatment strategies for low-risk papillary thyroid carcinoma: a position statement from the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism (SBEM)

Increasingly sensitive diagnostic methods, better understanding of molecular pathophysiology, and well-conducted prospective studies have changed the current approach to patients with thyroid cancer, requiring the implementation of individualized management. Most patients with papillary thyroid carcinoma (PTC) are currently considered to have a low risk of mortality and disease persistence/recurrence. Consequently, current treatment recommendations for these patients include less invasive or intensive therapies. We used the most recent evidence to prepare a position statement providing guidance for decisions regarding the management of patients with low-risk PTC (LRPTC). This document summarizes the criteria defining LRPTC (including considerations regarding changes in the TNM staging system), indications and contraindications for active surveillance, and recommendations for follow-up and surgery. Active surveillance may be an appropriate initial choice in selected patients, and the criteria to recommend this approach are detailed. A section is dedicated to the current evidence regarding lobectomy versus total thyroidectomy and the potential pitfalls of each approach, considering the challenges during long-term follow-up. Indications for radioiodine (RAI) therapy are also addressed, along with the benefits and risks associated with this treatment, patient preparation, and dosage. Finally, this statement presents the best follow-up strategies for LRPTC after lobectomy and total thyroidectomy with or without RAI.

A Joint Statement from the American Thyroid Association, the European Association of Nuclear Medicine, the European Thyroid Association, the Society of Nuclear Medicine and Molecular Imaging on Current Diagnostic and Theranostic Approaches in the Management of Thyroid Cancer

Background: The American Thyroid Association (ATA), the European Association of Nuclear Medicine, the European Thyroid Association, and the Society of Nuclear Medicine and Molecular Imaging have established an intersocietal working group to address the current controversies and evolving concepts in thyroid cancer management and therapy. The working group annually identifies topics that may significantly impact clinical practice and publishes expert opinion articles reflecting intersocietal collaboration, consensus, and suggestions for further research to address these important management issues. Summary: In 2019, the intersocietal working group identified the following topics for review and interdisciplinary discussion: (i) perioperative risk stratification, (ii) the role of diagnostic radioactive iodine (RAI) imaging in initial staging, and (iii) indicators of response to RAI therapy. Conclusions: The intersocietal working group agreed that (i) initial patient management decisions should be guided by perioperative risk stratification that should include the eighth edition American Joint Committee on Cancer staging system to predict disease specific mortality, the modified 2009 ATA risk stratification system to estimate structural disease recurrence, with judicious incorporation of molecular theranostics to further refine management recommendations; (ii) diagnostic RAI scanning in ATA intermediate risk patients should be utilized selectively rather than being considered mandatory or not necessary for all patients in this category; and (iii) a consistent semiquantitative reporting system should be used for response evaluations after RAI therapy until a reproducible and clinically practical quantitative system is validated.

Reappraising the Diagnostic Accuracy of Post-Treatment Whole-Body Scans for Differentiated Thyroid Carcinoma

Initial treatment for differentiated thyroid carcinoma (DTC) often consists of surgery and the administration of radioiodine. In this context, post-treatment Whole-Body Scans (ptWBS) are currently recommended, but data on its diagnostic accuracy are rare. The aim of the study was to evaluate the performance of ptWBS for distant metastasis in DTC patients. We included DTC patients who received radioiodine and underwent ptWBS between 2009-2015. The medical data were independently reviewed by two specialists to evaluate the concordance of positive distant ptWBS uptake and distant metastasis documented by imaging exams (gold standard). We studied 268 DTC patients. The mean age was 46±16 years (82% women), and papillary thyroid carcinoma was diagnosed in 87% of the patients. The median tumor size was 2.7 cm, 40% had lymph node involvement, and 11% had distant metastasis. Twenty-eight patients (10%) had distant ptWBS uptake, and nine of them (32%) were false-positives. In addition, nine false-negative ptWBS uptakes were identified. The overall performance of ptWBS showed 68% sensitivity and 96% specificity with significantly different performance according to the American Thyroid Association (ATA) risk groups. While the ptWBS performance for ATA low-intermediate-risk showed 29% sensitivity, 97% specificity, and Kappa of 0.19, the ATA high-risk group ptWBS displayed high sensitivity (82%), specificity (100%), and good agreement (Kappa 0.74). ptWBS is useful for a subgroup of ATA high-risk DTC patients. The overall poor performance of ptWBS suggests that it should be reconsidered for routine use in ATA at low to intermediate risk: the exam has little value to this subgroup.

Preablation Diagnostic Whole-Body Scan vs Empiric Radioactive Iodine Ablation in Differentiated Thyroid Cancer: Cost-effectiveness Analysis

OBJECTIVE

To perform a comparative analysis of postthyroidectomy radioactive iodine ablation dosing with or without the implementation of a diagnostic whole-body scan in patients with well-differentiated thyroid cancer.

STUDY DESIGN

Decision analysis model.

SETTING

Hospital or ambulatory center.

METHODS

A decision tree model was created to determine the cost-effectiveness of radioactive iodine ablation dosed with diagnostic whole-body scans versus empiric radioactive iodine ablation in patients with differentiated thyroid cancer undergoing postthyroidectomy ablation. The decision tree was populated with values from the published literature. Costs were represented by 2020 Medicare reimbursement rates (US dollars), and morbidity and survival data were used to calculate quality-adjusted life-years. The incremental cost-effectiveness ratio was the primary outcome.

RESULTS

Empiric radioactive iodine dosing was the dominant economic strategy, producing 0.94 more quality-adjusted life-years while costing $1250.07 less than management with a diagnostic whole-body scan. Sensitivity analyses upheld these results except in cases involving a large discrepancy in successful ablation rates between the diagnostic and empiric treatment arms.

CONCLUSION

For patients with differentiated thyroid cancer requiring postthyroidectomy ablation, it is more cost-effective to administer radioactive iodine empirically.

Efficacy of low radioiodine activity versus intermediate-high activity in the ablation of low-risk differentiated thyroid cancer

PURPOSE

The aim of our study was to compare the efficacy of thyroid remnant ablation using low (1.1 GBq) and intermediate-high radioiodine (RAI) activity (1.85-3.7 GBq) in low-risk differentiated thyroid carcinoma (DTC) and to evaluate the staging role of the whole body scan (WBS) in detection extrathyroidal disease.

MATERIALS AND METHODS

We retrospectively included 277 patients who underwent total thyroidectomy and RAI for low-risk DTC and divided them in two groups according to RAI activity at ablation: group 1 (n = 174) treated with low activity (1.1 GBq), and group 2 (n = 103) with intermediate-high activity (1.85-3.7 GBq). To evaluate the successful ablation rate, the WBS 1 year after RAI was visually interpreted using a three-point scale: score 0 in case of absence of visible RAI uptake in thyroid bed; score 1 in presence of faint uptake in the thyroid bed; and score 2 in case of significant RAI uptake in thyroid bed.

RESULTS

The success ablation rate was significantly higher in group 2 than group 1 (p < 0.001) with the presence of a positive WBS (score 1-2) in 65% low-activity group and 33% in intermediate-high group. Considering response to therapy categories, excellent response rate was significantly higher in group 2 (p = 0.020), while indeterminate response was higher in group 1 (p value = 0.005). Post RAI imaging revealed extrathyroidal uptake in 27 cases: 17 laterocervical nodal and 10 distant metastases. In both groups similar detection rate of nodal and distant metastases were recognized without any statistical difference.

CONCLUSIONS

The ablation rate with intermediate-high RAI activity (1.85-3.7 GBq) was better than with a low activity (1.1 GBq). First WBS may help to recognize nodal and distant metastases in about 10% of cases changing clinical stage and subsequent management.

Evaluation of the 2015 ATA Guidelines in Patients With Distant Metastatic Differentiated Thyroid Cancer

CONTEXT

Current American Thyroid Association (ATA) Management Guidelines for the treatment of differentiated thyroid cancer (DTC) stratify patients to decide on additional radioiodine (RAI) therapy after surgery, and to predict recurring/persisting disease. However, studies evaluating the detection of distant metastases and how these guidelines perform in patients with distant metastases are scarce.

OBJECTIVE

To evaluate the 2015 ATA Guidelines in DTC patients with respect to 1) the detection of distant metastases, and 2) the accuracy of its Risk Stratification System in patients with distant metastases.

PATIENTS AND MAIN OUTCOME MEASURES

We retrospectively included 83 DTC patients who were diagnosed with distant metastases around the time of initial therapy, and a control population of 472 patients (312 low-risk, 160 intermediate-risk) who did not have a routine indication for RAI therapy. We used the control group to assess the percentage of distant metastases that would have been missed if no RAI therapy was given.

RESULTS

Two hundred forty-six patients had no routine indication for RAI therapy of which 4 (1.6%) had distant metastases. Furthermore, among the 83 patients with distant metastases, 14 patients (17%) had excellent response, while 55 (67%) had structural disease after a median follow-up of 62 months. None of the 14 patients that achieved an excellent response had a recurrence.

CONCLUSIONS

In patients without a routine indication for RAI therapy according to the 2015 ATA Guidelines, distant metastases would initially have been missed in 1.6% of the patients. Furthermore, in patients with distant metastases upon diagnosis, the 2015 ATA Guidelines are an excellent predictor of both persistent disease and recurrence.