ENDOCRINE TUMOURS: Imaging in the follow-up of differentiated thyroid cancer: current evidence and future perspectives for a risk-adapted approach

Radioactive Iodine Therapy in Differentiated Thyroid Cancer: An Update on Dose Recommendations and Risk of Secondary Primary Malignancies

Radioactive iodine (RAI) therapy with iodine-131 is performed in select cases of differentiated thyroid cancer (DTC), typically for remnant ablation, adjuvant therapy, or treatment of known persistent disease. Herein, we review updated RAI dose recommendations and associated risks of secondary primary malignancy (SPM). RAI dose is usually chosen empirically based on the risk assessment of tumor recurrence and other factors. Dose recommendations differ slightly among relevant medical societies. As of April 2024, most medical societies, including the American Thyroid Association (ATA), European Thyroid Association (ETA), Society of Nuclear Medicine and Molecular Imaging/European Association of Nuclear Medicine (SNMMI/ EANM), and National Comprehensive Cancer Network (NCCN), recommend a dose of 1.11 GBq (30 mCi) I-131 for remnant ablation. For adjuvant therapy, the recommended RAI dose ranges from 1.11 to 3.7 GBq (30-100) mCi I-131, although doses up to 5.6 GBq (150 mCi) may also be considered. In patients with known or suspected metastatic disease, at least 3.7 GBq (100 mCi) I-131 should be administered, and RAI doses as high as 7.4 GBq (200 mCi) may be justified depending on the suspected tumor burden and extent. Dosimetry has the advantage of tailoring the RAI dose to each patient's pharmacokinetics, resulting in ≥ 7.4 GBq (200 mCi) of I-131 in most cases. There is an ongoing debate about the risk of developing SPM due to RAI therapy, with several multicenter studies and meta-analyses concerning SPM being published in the last 2 years. The incidence of RAI-associated SPM varies according to the study design and detection method. Several studies showed no increased incidence, and there was no specific secondary cancer or cancer group linked to RAI exposures. Some reports indicated that cumulative RAI doses exceeding 5.6-7.4 GBq (150-200 mCi) were found to represent an increased risk for developing SPM. However, a clearly defined dose threshold cannot be provided based on the current literature. Nonetheless, caution should be exercised when considering repeated RAI therapies for persistent metastatic PTC, with a cumulative dose exceeding 37.0 GBq (1,000 mCi), due to the potential risk of developing SPM and other long-term toxicity. Further research is warranted to understand better the relationship between RAI dose and the risk of SPM.

Follow-up strategy of radiofrequency ablation for papillary thyroid microcarcinoma: defining a response-to-ablation system

OBJECTIVE

To define a response-to-ablation system based on dynamic risk stratification proposed by the 2015 American Thyroid Association guidelines for predicting clinical outcomes and guiding follow-up strategies for patients with low-risk papillary thyroid microcarcinoma (PTMC) who underwent radiofrequency ablation (RFA).

METHODS

This retrospective study reviewed patients with low-risk PTMC who underwent RFA between 2014 and 2018. We classified patients into three groups based on their response to therapy at the 1-year follow-up: complete, indeterminate, and incomplete. The primary endpoints were local tumor progression (LTP) and disease-free survival (DFS).

RESULTS

Among the 748 patients (mean age, 43.7 years ± 9.8; 586 women), 4.0% (30/748) had LTP during a median follow-up of 5 years. The response was complete in 80.2% (600/748) of the patients, indeterminate in 18.1% (135/748), and incomplete in 1.7% (13/748). The LTP rate in the final follow-up was 1% (6/600), 8.1% (11/135), and 100% (13/13), respectively. The risk of LTP was significantly different in the incomplete response group (HR, 1825.82; 95% CI: 458.27, 7274.36; p < 0.001) and indeterminate response group (HR, 8.12; 95% CI: 2.99, 22.09; p < 0.001) than in the complete response group. There were significant differences in DFS among groups (p < 0.001). The proportion of variation explained and C-index of the system was high (27.66% and 0.79, respectively).

CONCLUSIONS

We defined a response-to-ablation system that provides a new paradigm for the management of patients with PTMC who underwent RFA. Our data confirm that the system can effectively predict the risk of LTP and guide ongoing follow-up recommendations.

KEY POINTS

• The response-to-ablation system can classify patients with low-risk PTMC who underwent RFA into complete, indeterminate, or incomplete response categories. • Results suggest that, in this population, this system can identify three separate cohorts of patients who have significantly different clinical outcomes. • The response-to-ablation system will help better tailor the ongoing follow-up recommendations.

Thyroglobulin Value Predict Iodine-123 Imaging Result in Differentiated Thyroid Cancer Patients

Background: In differentiated thyroid cancer (DTC) patients, the response to initial treatments is evaluated 6-12 months after radioiodine therapy (RIT) according to the 2015 American Thyroid Association (2015 ATA) criteria. In selected patients, diagnostic 131-radioiodine whole-body scintigraphy (Dx-WBS) is recommended. We evaluated the diagnostic performance of ¹²³I-Dx-WBS-SPECT/CT imaging in detecting incomplete structural responses in the early follow-up of DTC patients and, additionally, derived optimized basal-Tg value as a yardstick for scintigraphic imaging. Methods: We reviewed the records of 124 low or intermediate-risk DTC patients with negative anti-thyroglobulin antibody. All patients had undergone (near)-total-thyroidectomy followed by RIT. The response to initial treatments was evaluated 6-12 months after RIT. Results: According to the 2015 ATA criteria, 87, 19 and 18 DTC patients were classified to have excellent response (ER), indeterminate/incomplete biochemical response (BIndR/BIR) or structural incomplete response (SIR), respectively. Among patients with less than ER, 18 had a positive ¹²³I-Dx-WBS-SPECT/CT. Metastatic disease at ¹²³I-Dx-WBS-SPECT/CT mainly involved lymph nodes within the central compartment, and corresponding neck ultrasound examinations were negative. The ROC curve analysis was performed to define the best basal-Tg cut-off (i.e., 0.39 ng/mL; AUC = 0.852) able to discriminate patients with and without positive ¹²³I-Dx-WBS-SPECT/CT, respectively. The overall sensitivity, specificity, accuracy, PPV and NPV were 77.8%, 89.6%, 87.9%, 56.0% and 95.9%, respectively. Basal-Tg cut-off was an independent risk factor for having a positive ¹²³I-Dx-WBS-SPECT/CT. Conclusion:¹²³I-Dx-WBS-SPECT/CT identified lymph node metastases in 14/37 patients with less than ER and a negative neck ultrasound, thus modifying the management of such patients. The diagnostic performance of ¹²³I-Dx-WBS-SPECT/CT significantly increased in patients with basal-Tg values ≥ 0.39 ng/mL.

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.

Incorporation of a machine learning pathological diagnosis algorithm into the thyroid ultrasound imaging data improves the diagnosis risk of malignant thyroid nodules

Objective

This study aimed at establishing a new model to predict malignant thyroid nodules using machine learning algorithms.

Methods

A retrospective study was performed on 274 patients with thyroid nodules who underwent fine-needle aspiration (FNA) cytology or surgery from October 2018 to 2020 in Xianyang Central Hospital. The least absolute shrinkage and selection operator (lasso) regression analysis and logistic analysis were applied to screen and identified variables. Six machine learning algorithms, including Decision Tree (DT), Extreme Gradient Boosting (XGBoost), Gradient Boosting Machine (GBM), Naive Bayes Classifier (NBC), Random Forest (RF), and Logistic Regression (LR), were employed and compared in constructing the predictive model, coupled with preoperative clinical characteristics and ultrasound features. Internal validation was performed by using 10-fold cross-validation. The performance of the model was measured by the area under the receiver operating characteristic curve (AUC), accuracy, precision, recall, F1 score, Shapley additive explanations (SHAP) plot, feature importance, and correlation of features. The best cutoff value for risk stratification was identified by probability density function (PDF) and clinical utility curve (CUC).

Results

The malignant rate of thyroid nodules in the study cohort was 53.2%. The predictive models are constructed by age, margin, shape, echogenic foci, echogenicity, and lymph nodes. The XGBoost model was significantly superior to any one of the machine learning models, with an AUC value of 0.829. According to the PDF and CUC, we recommended that 51% probability be used as a threshold for determining the risk stratification of malignant nodules, where about 85.6% of patients with malignant nodules could be detected. Meanwhile, approximately 89.8% of unnecessary biopsy procedures would be saved. Finally, an online web risk calculator has been built to estimate the personal likelihood of malignant thyroid nodules based on the best-performing ML-ed model of XGBoost.

Conclusions

Combining clinical characteristics and features of ultrasound images, ML algorithms can achieve reliable prediction of malignant thyroid nodules. The online web risk calculator based on the XGBoost model can easily identify in real-time the probability of malignant thyroid nodules, which can assist clinicians to formulate individualized management strategies for patients.

Revision Thyroid Surgery

The incidence of recurrence in well-differentiated thyroid malignancies range from 10 to 30%. It is estimated that about 31-46% of patients with differentiated thyroid cancer will have the persistent disease and 1.2-6.8% will have structural recurrences during post-operative monitoring, depending on the initial therapy and prognostic variables. It is challenging to decide on treatment versus active monitoring following repeated or persistent tumour detection. The biological factors of the tumour and the patient guide us in the overall decision-making. Revision thyroid surgery is technically challenging. The morbidity encountered during the revision surgery is related to the anatomy of the region undergoing dissection, the degree of fibrosis and scarring from prior surgery and the operating surgeon's experience. Successful comprehensive management of revision thyroid surgery needs a multi-disciplinary approach. This review article highlights the definition, indications for revision surgery, identification of recurrent disease, management of parathyroid and recurrent laryngeal nerves with neuromonitoring.

Stereotactic Radiosurgery for Differentiated Thyroid Cancer Brain Metastases: An International, Multicenter Study

Background: Brain metastases (BM) from differentiated thyroid cancer are rare. Stereotactic radiosurgery (SRS) is commonly used for the treatment of BMs; however, the experience with SRS for thyroid cancer BMs remains limited. The goal of this international, multi-centered study was to evaluate the efficacy and safety of SRS for thyroid cancer BMs. Methods: From 10 institutions participating in the International Radiosurgery Research Foundation, we pooled patients with established papillary or follicular thyroid cancer diagnosis who underwent SRS for histologically confirmed or radiologically suspected BMs. We investigated patient overall survival (OS), local tumor control, and adverse radiation events (AREs). Results: We studied 42 (52% men) patients who underwent SRS for 122 papillary (83%) or follicular (17%) thyroid cancer BMs. The mean age at SRS was 59.86 ± 12.69 years. The mean latency from thyroid cancer diagnosis to SRS for BMs was 89.05 ± 105.49 months. The median number of BMs per patient was 2 (range: 1-10 BMs). The median SRS treatment volume was 0.79 cm³ (range: 0.003-38.18 cm³), and the median SRS prescription dose was 20 Gy (range: 8-24 Gy). The median survival after SRS for BMs was 14 months (range: 3-58 months). The OS was significantly shorter in patients harboring ≥2 BMs, when compared with patients with one BM (Log-rank = 5.452, p = 0.02). Two or more BMs (odds ratio [OR] = 3.688; confidence interval [CI]: 1.143-11.904; p = 0.03) and lower Karnofsky performance score at the time of SRS (OR = 0.807; CI: 0.689-0.945; p = 0.008) were associated with shorter OS. During post-SRS imaging follow-up of 25.21 ± 30.49 months, local failure (progression and/or radiation necrosis) of BMs treated with SRS was documented in five (4%) BMs at 7.2 ± 7.3 months after the SRS. At the last imaging follow-up, the majority of patients with available imaging data had stable intracranial disease (33%) or achieved complete (26%) or partial (24%) response. There were no clinical AREs. Post-SRS peritumoral T2/fluid attenuated inversion recovery signal hyperintensity was noted in 7% BMs. Conclusion: The SRS allows durable local control of papillary and follicular thyroid cancer BMs in the vast majority of patients. Higher number of BMs and worse functional status at the time of SRS are associated with shorter OS in patients with thyroid cancer BMs. The SRS is safe and is associated with a low risk of AREs.

Can shear wave elastography determine remnant thyroid tissue in the early postoperative period in patients with differentiated thyroid carcinoma?

PURPOSE

This study aims to investigate the usability of ultrasonography (US) and shear wave elastography (SWE) in detecting remnant thyroid tissue (RTT) within the first three postoperative months in patients who underwent total thyroidectomy (TT) for differentiated thyroid cancer (DTC) and who were scheduled for radioiodine (RAI) ablation therapy.

METHODS

Sixty-nine patients who underwent a TT operation due to DTC were included in the study. The participant's thyroid surgical bed was first evaluated by thyroid scintigraphy and then by greyscale US and SWE to investigate RTT. The participants were divided into two groups, those with and those without RTT. SWE quantitative data were compared between the two groups. Receiver operating characteristic (ROC) curve analysis was performed to determine the best cut-off values for stiffness and velocity in distinguishing RTT.

RESULTS

A total of 149 regions were analysed in 69 participants (43 females, 26 males). The average time elapsed after the operation was 65.2 ± 24.1 days. RTT was determined by scintigraphy and US-SWE in 38 (55%) patients. The stiffness and velocity values were significantly higher in the group with RTT than in the group without RTT. To distinguish RTT from the thyroid bed, the best cut-off values for stiffness and velocity were 15.7 kPa and 2.12 m/s, respectively.

CONCLUSIONS

US with SWE can detect RTT in the early postoperative period in patients who have undergone TT due to DTC and who are scheduled for RAI treatment. The use of US and SWE will be particularly beneficial in patients with RTT but who have false-negative Tg levels and RTT that is not I-131 avid.

Selective Use of Radioactive Iodine Therapy for Papillary Thyroid Cancers With Low or Lower-Intermediate Recurrence Risk

CONTEXT

Current guidelines recommend a selective use of radioiodine treatment (RAI) for papillary thyroid cancer (PTC).

OBJECTIVE

This work aimed to determine how policy changes affect the use of RAI and the short-term outcomes of patients.

METHODS

A retrospective analysis of longitudinal data was conducted in an academic referral center of patients with nonaggressive PTC variants; no extrathyroidal invasion or limited to soft tissues, no distant metastases, and 5 or fewer central-compartment cervical lymph node metastases. In cohort 1, standard treatments were total thyroidectomy and RAI (May 2005-June 2011); in cohort 2 decisions on RAI were deferred for approximately 12 months after surgery (July 2011-December 2018). Propensity score matching was used to adjust for sex, age, tumor size, lymph node status, and extrathyroidal extension. Intervention included immediate RAI or deferred choice. Main outcome measures were responses to initial treatment during 3 or more years of follow-up.

RESULTS

In cohort 1, RAI was performed in 50 of 116 patients (51.7%), whereas in cohort 2, it was far less frequent: immediately in 10 of 156 (6.4%), and in 3 more patients after the first follow-up data. The frequencies of structural incomplete response were low (1%-3%), and there were no differences between the 2 cohorts at any follow-up visit. Cohort 2 patients had higher rates of "gray-zone responses" (biochemical incomplete or indeterminate response).

CONCLUSION

Selective use of RAI increases the rate of patients with "uncertain" status during early follow-up. The rate of structural incomplete responses remains low regardless of whether RAI is used immediately. Patients should be made aware of the advantages and drawbacks of omitting RAI.

Primary lung cancer with radioiodine avidity: A thyroid cancer cohort study

BACKGROUND

A proportion of lung cancers show sodium/iodide symporter (NIS) expression. Lung cancers with NIS expression may uptake radioiodine (RAI) and show RAI-avid lesions on RAI scan for differentiated thyroid cancer (DTC) surveillance.

AIM

To investigate the possibility of RAI uptake by lung cancer in a cohort with thyroid cancer.

METHODS

RAI-avid lung cancers were analyzed using a prospectively maintained database of patients with thyroid cancer who were registered at a medical center between December 1, 1976 and May 28, 2018. NIS expression in lung cancer was assessed using immunohistochemical staining.

RESULTS

Of the 5000 patients with thyroid cancer from the studied dataset, 4602 had DTC. During follow-up, 33 patients developed primary lung cancer. Of these patients, nine received an iodine-131 (¹³¹I) scan within 1 year before the diagnosis of lung cancer. One of these nine lung cancers was RAI-avid. NIS expression was evaluated, and three of the eight available lung cancers revealed NIS expression. The proportions of lung cancer cells with NIS expression were 60%, 15%, and 10%. The RAI-avid lung cancer had the highest level of expression (60%). The RAI-avid lung cancer had a spiculated border upon single-photon emission computed tomography/computed tomography, which led to an accurate diagnosis.

CONCLUSION

A proportion of lung cancer demonstrates NIS expression and is RAI-avid. Clinicians should be aware of this possibility in the interpretation of RAI scintigraphy.

Ultrasound Surveillance of Abnormal Cervical Lymph Nodes in Patients With Papillary Thyroid Carcinoma After Surgery

OBJECTIVES

To document the changing trends of abnormal cervical lymph nodes (LNs) in patients with papillary thyroid carcinoma (PTC) who had serial follow-up ultrasound (US) scans after surgery and to determine how these node abnormalities progress in real time.

METHODS

Ultrasound findings from 568 consecutive patients with PTC who were monitored postoperatively were reviewed. Abnormal LNs were classified as either suspicious or indeterminate according to the European Thyroid Association guidelines. Outcomes from US monitoring of the LNs were recorded and analyzed.

RESULTS

Seventy-six (13.4%) of 568 patients were identified with abnormal LNs. Among them, 55 (72.4%) were initially found to have suspicious LNs, and the other 21 (27.6%) had indeterminate lesions. Of the 55 suspicious LNs, final scans showed that 38 (69.1%) lesions were still suspicious, whereas the remaining 17 (30.9%) nodes were shown to have resolved after a median follow-up of 36 months. Of the 21 indeterminate node abnormalities, final scans showed that 16 (76.2%) LNs remained indeterminate, whereas the other 5 (23.8%) nodes had developed into suspicious LNs after a median follow-up of 44 months. Loss of the fatty hilum and peripheral or diffusedly increased vascularity were more likely to be linked to persistent suspicious LNs (P = .02 and .04, respectively). Suspicious LNs with echogenic foci but a lack of other abnormal features were more frequently found to have resolved thereafter (P = .03).

CONCLUSIONS

Abnormal LNs detected after PTC surgery can often remain indolent during US surveillance, and a small portion of the nodes would have resolved over time.

Personalized management of differentiated thyroid cancer in real life - practical guidance from a multidisciplinary panel of experts

PURPOSE

The standard of care for differentiated thyroid carcinoma (DTC) includes surgery, risk-adapted postoperative radioiodine therapy (RaIT), individualized thyroid hormone therapy, and follow-up for detection of patients with persistent or recurrent disease. In 2019, the nine Martinique Principles for managing thyroid cancer were developed by the American Thyroid Association, European Association of Nuclear Medicine, Society of Nuclear Medicine and Molecular Imaging, and European Thyroid Association. In this review, we present our clinical practice recommendations with regard to implementing these principles in the diagnosis, treatment, and long-term follow-up of patients with DTC.

METHODS

A multidisciplinary panel of five thyroid cancer experts addressed the implementation of the Martinique Principles in routine clinical practice based on clinical experience and evidence from the literature.

RESULTS

We provide a suggested approach for the assessment and diagnosis of DTC in routine clinical practice, including the use of neck ultrasound, measurement of serum thyroid-stimulating hormone and calcitonin, fine-needle aspiration, cytology, and molecular imaging. Recommendations for the use of surgery (lobectomy vs. total thyroidectomy) and postoperative RaIT are also provided. Long-term follow-up with neck ultrasound and measurement of serum anti-thyroglobulin antibody and basal/stimulated thyroglobulin is standard, with ¹²³/¹³¹I radioiodine diagnostic whole-body scans and ¹⁸F-fluoro-2-deoxyglucose positron emission tomography/computed tomography suggested in selected patients. Management of metastatic DTC should involve a multidisciplinary team.

CONCLUSIONS

In routine clinical practice, the Martinique Principles should be implemented in order to optimize clinical management/outcomes of patients with DTC.

The Impact of Arterial Phase on the Detection of Cervical Lymph Node Metastasis From Papillary Thyroid Carcinoma: A Quantitative Evaluation on Multiphasic Computed Tomography

OBJECTIVE

The purpose of this study was to assess the diagnostic performance of multiphasic computed tomography (CT) in the discrimination of metastatic lymph nodes (LNs) of papillary thyroid cancer by using quantitative parameters.

METHODS

This study enrolled 272 pathologically proven metastatic and benign LNs. Multiphasic CT was utilized by using nonenhanced, arterial (25-second delay), and venous (80-second delay) phases. Mean tissue attenuation values (MAVs) of metastatic and benign LNs were measured, and normalized MAV (common carotid artery and paraspinal muscle) and wash-in and wash-out percentages were also calculated.

RESULTS

The arterial phase showed the highest diagnostic performance in differentiation (area under the curve ± standard error, 0.97 ± 0.02; 95% confidence interval, 0.94-1.0; P < 0.001). Cutoff values for MAVs, normalized MAVs, and wash-in and wash-out percentages to predict metastatic LNs were calculated as 109 HU, 0.33, 1.93, 122.5, and -5.6 (sensitivity: 93.4%, 93.3%, 90.4%, 94.1%, and 97.8%, and specificity: 99.3%, 90.4%, 98.5%, 92.6%, and 99.3%, respectively).

CONCLUSIONS

Early-phase enhanced CT and the use of quantitative parameters derived from multiphasic CT improve the detection of cervical lymph node metastasis from papillary thyroid cancer.

Taller-Than-Wide Shape: A New Definition Improves the Specificity of TIRADS Systems

INTRODUCTION

A taller-than-wide (TTW) shape is a suspicious feature of thyroid nodules commonly defined as an anteroposterior/transverse diameter (AP/T) ratio >1. An intraobserver variability of up to 18% in AP diameter evaluations has been described, which may lead to overreporting of this feature. To potentially improve the reliability of the TTW definition, we propose an arbitrary ratio of ≥1.2.

OBJECTIVE

The aim of this study was to estimate the impact of this definition on diagnostic performance.

METHODS

We prospectively analyzed 553 thyroid nodules referred for cytology evaluation at an academic center. Before fine-needle aspiration, two examiners jointly defined all sonographic features considered in risk stratification systems developed by the American Thyroid Association (ATA), the American Association of Clinical Endocrinologists (AACE), the American College of Radiology (ACR TIRADS), the European Thyroid Association (EU-TIRADS), and the Korean Society of Thyroid Radiology (K-TIRADS). TTW was defined according to the current definition (AP/T diameter ratio >1) and an arbitrary alternative definition (AP/T ratio >1.2).

RESULTS

The alternative definition classified fewer nodules as TTW (28, 5.1% vs. 94, 17%). The current and proposed definitions have a sensitivity of 26.2 and 11.9% (p = 0.03) and a specificity of 83.8 and 95.5% (p < 0.001). Thus, as a single feature, the arbitrary definition has a lower sensitivity and a higher specificity. When applied to sonographic risk stratification systems, however, the proposed definition would increase the number of avoided biopsies (up to 58.2% for ACR TIRADS) and the specificity of all systems, without negative impact on sensitivity or diagnostic odds ratio.

CONCLUSIONS

Re-defining TTW nodules as those with an AP/T ratio ≥1.2 improves this marker's specificity for malignancy. Using this definition in risk stratification systems will increase their specificity, reducing the number of suggested biopsies without significantly diminishing their overall diagnostic performance.

Contemporary Debates in Adult Papillary Thyroid Cancer Management

An ever-increasing population of patients with papillary thyroid cancer is engaging with health care systems around the world. Numerous questions about optimal management have arisen that challenge conventional paradigms. This is particularly the case for patients with low-risk disease, who comprise most new patients. At the same time, new therapies for patients with advanced disease are also being introduced, which may have the potential to prolong life. This review discusses selected controversial issues in adult papillary thyroid cancer management at both ends of the disease spectrum. These topics include: (i) the role of active surveillance for small papillary cancers; (ii) the extent of surgery in low-risk disease (lobectomy vs total thyroidectomy); (iii) the role of postoperative remnant ablation with radioiodine; (iv) optimal follow-up strategies in patients, especially those who have only undergone lobectomy; and (v) new therapies for advanced disease. Although our current management is hampered by the lack of large randomized controlled trials, we are fortunate that data from ongoing trials will be available within the next few years. This information should provide additional evidence that will decrease morbidity in low-risk patients and improve outcomes in those with distant metastatic disease.

Thyroid Cancer Patients With No Evidence of Disease: The Need for Repeat Neck Ultrasound

CONTEXT

Ultrasonography (US) is considered the most sensitive tool for imaging persistent or recurrent papillary thyroid cancer (PTC) in the neck.

OBJECTIVE

To clarify the usefulness of routine neck US in low- and intermediate-risk patients with PTC with no evidence of disease 1 year after thyroidectomy.

DESIGN

Retrospective analysis of prospectively recorded data.

SETTING

Academic center.

PATIENTS

Two hundred twenty-six patients with PTC with sonographically normal neck lymph nodes and unstimulated serum thyroglobulin (Tg) levels that were either undetectable (<0.20 ng/mL) or low (0.21 to 0.99 ng/mL) at the 1-year evaluation.

INTERVENTIONS

Yearly assessment: unstimulated serum Tg level, anti-Tg-antibody (TgAb) titer, TSH levels, and ultrasound examination of neck lymph nodes.

MAIN OUTCOME MEASURES

Rates of ultrasonographic lymph node abnormalities at the 3-year and last follow-up visits.

RESULTS

In patients with an undetectable Tg level at the 1-year evaluation, sonographically suspicious neck lymph nodes were found in 1.2% of patients at 3 years and in 1.8% at the last visit [negative predictive values (NPVs) of 1-year Tg < 0.2 ng/mL: 98.8% (95% CI 95.8% to 99.9%) and 98.2% (95% to 99.6%), respectively]. Similar NPVs emerged for low detectable 1-year Tg levels [98.2% (90.3% to 99.9%) and 94.5% (84.9% to 98.9%) at the 3-year and last visits, respectively]. Seventy-five percent of the nodal lesions were likely false positive; none required treatment.

CONCLUSIONS

Low- and intermediate-risk patients with PTC with negative ultrasound findings and unstimulated Tg levels <1 ng/mL at the 1-year evaluation can be safely followed with clinical assessments and unstimulated serum Tg determinations. Neck US might be repeated if TgAb titers rise, or unstimulated Tg levels exceed 1 ng/mL.

Orbital Radioiodine Uptake on Scintigraphy in a Patient with Thyroid Cancer

BACKGROUND

Orbital radioiodine uptake in patients with thyroid cancer is very uncommon with only a few reported cases, most of them being metastasis. The accumulation of ¹³¹I in nonthyroidal tissues and body fluids can lead to false-positive results in scintigraphy, which are sometimes difficult to differentiate from true metastases.

CASE REPORT

A post-therapy ¹³¹I whole-body (WBI) scintigraphy in an asymptomatic 57-year-old female with papillary thyroid carcinoma (PTC) previously treated with total thyroidectomy and 6 ablative radioiodine doses showed a focal uptake in the right eyeball region. The lesion, placed in the orbital space, was surgically removed, and histology revealed a conjunctival inclusion cyst.

DISCUSSION

Ocular and orbital metastases from thyroid cancer, as well as some non-neoplastic disorders or contamination, are possible causes for ¹³¹I uptake in the orbital region in scintigraphy. Conjunctival inclusion cyst is a condition associated with incidental ¹³¹I uptake that had not been reported before and should be ruled out as a non-metastatic cause of orbital radioiodine uptake in patients with PTC.

Reducing the Number of Unnecessary Thyroid Biopsies While Improving Diagnostic Accuracy: Toward the "Right" TIRADS

CONTEXT

The prevalence of thyroid nodules in the general population is increasingly high, and at least half of those biopsied prove to be benign. Sonographic risk-stratification systems are being proposed as "rule-out" tests that can identify nodules that do not require fine-needle aspiration (FNA) cytology.

OBJECTIVE

To comparatively assess the performances of five internationally endorsed sonographic classification systems [those of the American Thyroid Association, the American Association of Clinical Endocrinologists, the American College of Radiology (ACR), the European Thyroid Association, and the Korean Society of Thyroid Radiology] in identifying nodules whose FNAs can be safely deferred and to estimate their negative predictive values (NPVs).

DESIGN

Prospective study of thyroid nodules referred for FNA.

SETTING

Single academic referral center.

PATIENTS

Four hundred seventy-seven patients (358 females, 75.2%); mean (SD) age, 55.9 (13.9) years.

MAIN OUTCOME MEASURES

Number of biopsies classified as unnecessary, false-negative rate (FNR), sensitivity, specificity, predictive values, and diagnostic ORs for each system.

RESULTS

Application of the systems' FNA criteria would have reduced the number of biopsies performed by 17.1% to 53.4%. The ACR Thyroid Imaging Reporting and Data System (TIRADS) allowed the largest reduction (268 of 502) with the lowest FNR (NPV, 97.8%; 95% CI, 95.2% to 99.2%). Except for the Korean Society of Thyroid Radiology TIRADS, all other systems exhibited significant discriminatory performance but produced significantly smaller reductions in the number of procedures.

CONCLUSIONS

Internationally endorsed sonographic risk stratification systems vary widely in their ability to reduce the number of unnecessary thyroid nodule FNAs. The ACR TIRADS outperformed the others, classifying more than half the biopsies as unnecessary with a FNR of 2.2%.

Thyroid nodule recurrence following lobo-isthmectomy: incidence, patient's characteristics, and risk factors

PURPOSE

This study was aimed at assessing the incidence and timing of thyroid nodules recurrence, defined as appearance of new benign or malignant nodules in contralateral lobe in patients with benign thyroid nodules or thyroid microcarcinoma treated with lobo-isthmectomy. Patient's characteristics and risk factors associated with this phenomenon were also investigated.

METHODS

A retrospective study was performed by evaluating 413 patients undergoing lobo-isthmectomy with a minimum follow-up of 1 year. Clinical characteristics, surgical interventions and complications, histological diagnosis, and thyroid function at last follow-up were collected.

RESULTS

Single or multiple thyroid nodule recurrence equally occurred in 80 patients (23%) with a median time to relapse of ~ 5 years (range 0.3-34.5 years) after lobo-isthmectomy. Recurrence was significantly associated with younger age (< 46 years) and number of pregnancies in women. Development of hypothyroidism was not rare either (~ 10%) and appeared in 3-19 months; a preoperative TSH level > 2.43 mIU/L was associated with the need of l-thyroxin replacement therapy after surgery. The most frequent surgical complication was transient hypoparathyroidism (4.6%), while the rate of permanent hypoparathyroidism significantly increased in patients submitted to completion thyroidectomy (5.3%).

CONCLUSIONS

Thyroid nodules recurrence following lobo-isthmectomy is not a rare event and occurs within 5 years after surgery, more frequently in younger patients with family history of nodular goiter and in women with multiple pregnancies. Pre-surgical TSH levels may predict the development of post-surgical hypothyroidism, possibly improving the management of patients addressed to surgery.

IS IT WORTH SUPPRESSING TSH IN LOW- AND INTERMEDIATE-RISK PAPILLARY THYROID CANCER PATIENTS BEFORE THE FIRST DISEASE ASSESSMENT?

OBJECTIVE

Guidelines recommend thyroid-stimulating hormone (TSH) suppression before the first response to treatment assessment in papillary thyroid cancer (PTC) patients. The aim of this study was to assess the rate of structural disease (SD) in low- and intermediate-risk PTC patients according to TSH levels measured 1 year after primary treatment.

METHODS

A consecutive, prospective series of low- and intermediate-risk PTC patients with 3-years follow-up was collected. TSH, thyroglobulin (Tg), antithyroglobulin antibodies (TgAb), and neck ultrasonography (US) 1 and 3 years after primary treatment were analyzed. Recurrence risk and disease status at 1 year were defined according to the American Thyroid Association (ATA) guidelines and as the presence or absence of SD after 3 years. Patients were grouped according to TSH level at 1 year: group 1, TSH <0.1 μUI/mL; group 2, TSH 0.1 to 0.5 μUI/mL; group 3, 0.5 to 2 μUI/mL; and group 4 >2 μUI/mL.

RESULTS

This study included 263 patients (70.9% female, median age 47.2 years) of whom the risk of recurrence was low in 170 (65%), intermediate-low in 63 (24%), and intermediate-high in 30 (11%). The response to initial treatment at 1 year was excellent in 149 (57%), biochemical incomplete in 18 (7%), indeterminate in 84 (32%), and structural incomplete in 12 (4%). Group 1 consisted of 53 (20%) patients, group 2 of 85 (32%), group 3 of 61 (23%), and group 4 of 64 (24%). The rate of SD at 1 and 3 years from primary treatment was not significantly different between TSH groups.

CONCLUSION

TSH suppression before the first response to treatment assessment does not appear to influence the rate of SD evaluated 1 and 3 years after primary treatment.

ABBREVIATIONS

ATA = American Thyroid Association; DTC = differentiated thyroid cancer; FTC = follicular thyroid cancer; LT4 = levothyroxine; PTC = papillary thyroid cancer; SD = structural disease; Tg = thyroglobulin; TgAb = antithyroglobulin antibodies; TSH = thyroid-stimulating hormone; US = ultrasonography.

Follow-up of differentiated thyroid cancer - what should (and what should not) be done

The treatment paradigm for thyroid cancer has shifted from a one-size-fits-all approach to more personalized protocols that range from active surveillance to total thyroidectomy followed by radioiodine remnant ablation. Accurate surveillance tools are available, but follow-up protocols vary widely between centres and clinicians, owing to the lack of clear, straightforward recommendations on the instruments and assessment schedule that health-care professionals should adopt. For most patients (that is, those who have had an excellent response to the initial treatment and have a low or intermediate risk of tumour recurrence), an infrequent assessment schedule is sufficient (such as a yearly determination of serum levels of TSH and thyroglobulin). Select patients will benefit from second-line imaging and more frequent assessments. This Review discusses the strengths and weaknesses of the surveillance tools and follow-up strategies that clinicians use as a function of the initial treatment and each patient's risk of recurrence.

Sonographically Estimated Risks of Malignancy for Thyroid Nodules Computed with Five Standard Classification Systems: Changes over Time and Their Relation to Malignancy

BACKGROUND

Over 50% of newly diagnosed thyroid nodules are either cytologically benign or presumed to be benign on the basis of low-suspicion sonographic findings. The strategies used for their long-term surveillance are based mainly on the estimated residual risk of malignancy calculated with various ultrasonographic classification systems (e.g., Thyroid Image Reporting and Data Systems [TIRADS]). We conducted a longitudinal study to evaluate the temporal stability of the initial risk estimates computed with five widely used systems and to determine whether risk class increases during follow-up are indeed predictive of malignancy.

METHODS

We re-analyzed data prospectively collected at a single academic referral center on 232 patients (age: 54.1 ± 13.7 years) with 432 asymptomatic, sonographically or cytologically benign thyroid nodules at baseline (T0) and 122 new nodules that were present five years later (T5). At both time points, the sonographically estimated risk of malignancy was calculated as recommended by the American Association of Clinical Endocrinologists/American College of Endocrinology/Associazione Medici Endocrinologi, the American College of Radiologists' TIRADS, the American Thyroid Association's 2015 practice guidelines, the European Thyroid Association's TIRADS (EU-TIRADS), and the TIRADS of the Korean Society of Thyroid Radiology (K-TIRADS).

RESULTS

For 57 to 127 (13.2-29.4%) of the original nodules, depending on the system used, the estimated malignancy risk increased over the 5-year interval. Of the nodules whose baseline risk had not warranted cytological assessment, very few (6.3-8.3%) met the criteria for cytology at the 5-year evaluation. Biopsy was indicated for only 4 to 8 (3.3-6.6%) of the new nodules based on T5 risk estimates. Despite these changes, none of the 232 patients was ever diagnosed with a cancer.

CONCLUSIONS

Ultrasound-based risk classes of presumably benign thyroid nodules remain fairly stable over time, and changes warranting biopsy are rare indeed. The appearance of new nodules is a frequent event, but very few (<5%) are classified as high risk, and only the 3-7% meet the criteria for cytological assessment. Collectively, these findings support the view that patients with presumably benign thyroid nodules can be safely followed with less intensive protocols.

Follicular thyroid cancer and Hürthle cell carcinoma: challenges in diagnosis, treatment, and clinical management

Follicular thyroid cancer is the second most common differentiated thyroid cancer histological type and has been overshadowed by its more common counterpart-papillary thyroid cancer-despite its unique biological behaviour and less favourable outcomes. In this Review, we comprehensively review the literature on follicular thyroid cancer to provide an evidence-based guide to the management of these tumours, to highlight the lack of evidence behind guideline recommendations, and to identify changes and challenges over the past decades in diagnosis, prognosis, and treatment. We highlight that correct identification of cancer in indeterminate cytological samples is challenging and ultrasonographic features can be misleading. Despite certain unique aspects of follicular thyroid cancer presentation and prognosis, no specific recommendations exist for follicular thyroid cancer and Hürthle cell carcinoma in evidence-based guidelines. Efforts should be made to stimulate additional research in this field.

Undetectable or low (<1 ng/ml) postsurgical thyroglobulin values do not rule out metastases in early stage differentiated thyroid cancer patients

Background

Differentiated thyroid cancer (DTC) work-up is based on (near)total-thyroidectomy plus thyroid remnant ablation (TRA) with 131-radioiodine in many patients, and long-life follow-up. ¹³¹I-post therapy whole body scan (pT-WBS) and serum thyroglobulin (Tg) are used in identifying metastatic patients. Some authors have evaluated the possibility of using post-surgical Tg (ps-Tg) values in deciding for or against TRA. The aim of our study was to verify the diagnostic accuracy of ¹³¹I-pT-WBS and SPECT/CT imaging (post-therapeutic imaging) compared to serum Tg levels in detecting metastases in early stage of DTC patients.

Results

Post-therapeutic imaging revealed metastases in 82 out of 570 (14.4%) patients. Metastases were successively confirmed by other diagnostic tools or by histology (sensitivity and PPV = 100%). Seventy-three out of 82 patients (90.2%) showed ps-Tg levels ≤1 ng/ml. In fifty-four per cent of patients, serum Tg levels at TRA remained ≤1 ng/ml.

Conclusion

In conclusion, ps-Tg levels cannot be used in deciding for or against TRA. In early stage of DTC, post-therapeutic imaging (¹³¹I-pT-WBS and SPECT/CT) is an accurate method of detecting metastases, also in patients with stimulated serum Tg values ≤1 ng/ml

Methods

We retrospectively reviewed the records of 570 consecutive patients affected by pT1-pT3 DTC (F = 450, M = 120), referred to our Nuclear Medicine Units in the last five years to perform TRA after (near)-total-thyroidectomy.All patients underwent TRA 3-4 months after thyroid surgery either in euthyroid or in hypothyroid state. Serum Tg values evaluated in post-surgical period and at TRA were matched with post-therapeutic imaging results.

Recent advances in managing differentiated thyroid cancer

The main clinical challenge in the management of thyroid cancer is to avoid over-treatment and over-diagnosis in patients with lower-risk disease while promptly identifying those patients with more advanced or high-risk disease requiring aggressive treatment. In recent years, novel clinical and molecular data have emerged, allowing the development of new staging systems, predictive and prognostic tools, and treatment approaches. There has been a notable shift toward more conservative management of low- and intermediate-risk patients, characterized by less extensive surgery, more selective use of radioisotopes (for both diagnostic and therapeutic purposes), and less intensive follow-up. Furthermore, the histologic classification; tumor, node, and metastasis (TNM) staging; and American Thyroid Association risk stratification systems have been refined, and this has increased the number of patients in the low- and intermediate-risk categories. There is now a need for new, prospective data to clarify how these changing practices will impact long-term outcomes of patients with thyroid cancer, and new follow-up strategies and biomarkers are still under investigation. On the other hand, patients with more advanced or high-risk disease have a broader portfolio of options in terms of treatments and therapeutic agents, including multitarget tyrosine kinase inhibitors, more selective BRAF or MEK inhibitors, combination therapies, and immunotherapy.

Interobserver agreement of various thyroid imaging reporting and data systems

Ultrasonography is the best available tool for the initial work-up of thyroid nodules. Substantial interobserver variability has been documented in the recognition and reporting of some of the lesion characteristics. A number of classification systems have been developed to estimate the likelihood of malignancy: several of them have been endorsed by scientific societies, but their reproducibility is yet to be assessed. We evaluated the interobserver variability of the AACE/ACE/AME, ACR, ATA, EU-TIRADS and K-TIRADS classification systems and the interobserver concordance in the indication to FNA biopsy. Two raters independently evaluated 1055 ultrasound images of thyroid nodules identified in 265 patients at multiple time points, in two separate sets (501 and 554 images). After the first set of nodules, a joint reading was performed to reach a consensus in the feature definitions. The interobserver agreement (Krippendorff alpha) in the first set of nodules was 0.47, 0.49, 0.49, 0.61 and 0.53, for AACE/ACE/AME, ACR, ATA, EU-TIRADS and K-TIRADS systems, respectively. The agreement for the indication to biopsy was substantial to near-perfect, being 0.73, 0.61, 0.75, 0.68 and 0.82, respectively (Cohen's kappa). For all systems, agreement on the nodules of the second set increased. Despite the wide variability in the description of single ultrasonographic features, the classification systems may improve the interobserver agreement that further ameliorates after a specific training. When selecting nodules to be submitted to FNA biopsy, that is main purpose of these classifications, the interobserver agreement is substantial to almost perfect.

Prognostic role of FDG PET/CT in patients with differentiated thyroid cancer treated with 131-iodine empiric therapy

BACKGROUND

To assess the long-term prognostic value of F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with differentiated thyroid carcinoma (DTC) undergoing empiric radioiodine (RAI) therapy due to raising values of thyroglobulin (Tg).

METHODS

Forty-nine patients with histological diagnosis of DTC (31 with papillary and 18 with follicular carcinoma) follow-up for a mean period of 7.9 ± 5 years after empiric RAI therapy were retrospectively analyzed.

RESULTS

FDG-PET/CT was negative in 15 (30.6%) patients and positive in 34 (69.4%), whereas postradioiodine therapy whole body scan (t-WBS) was negative in 16 (32.7%) and positive in 33 (67.3%) patients. FDG-PET/CT and t-WBS were in agreement in 32 patients (7 both negative and 25 both positive); on the contrary, in 17 patients there was disagreement between FDG-PET/CT and t-WBS (P =ns). At short-term follow-up, Tg normalized in 19 (38.8%) patients and was unchanged or increased in 30 (61.2%). Of the 15 patients with negative FDG-PET/CT, 11 (73.3%) showed Tg normalization, whereas of the 34 patients with positive FDG-PET/CT, only 8 (23.5%) had Tg normalization (χ =8.9, P < .005). At multivariate analysis, FDG-PET/CT and Tg normalization at short-term follow-up were independent predictors of disease-free survival (χ =26.3, P < .0001), while Tg normalization was the only variable associated with overall survival χ =7.2, P < .01).

CONCLUSION

FDG-PET/CT in association with Tg normalization at short-term follow-up may be useful for long-term prognostic stratification in DTC patients.

Impact of Radioguided Occult Lesion Localization (ROLL) in the management of cervical recurrences from differentiated thyroid cancer

BACKGROUND

Surgery is the elective treatment for cervical relapse from differentiated thyroid cancer (DTC) but it is technically challenging, with risk of failure and morbidity. We explored the feasibility and the efficacy of Radioguided Occult Lesion Localization (ROLL) with intratumoral 99mTc radiolabeled human albumin macroaggregates ([99mTc]MAA) injection in this setting.

METHODS

Fifteen patients who underwent ROLL by ultrasonography (US)-guided intratumoral injection of [99mTc]MAA between December 2013 and October 2016 for DTC recurrence were considered for this study. An hand-held gamma-probe was employed for intrasurgical lesion detection. Mini-invasive ROLL-guided excision for soft tissue recurrence and ROLL-assisted modified radical neck dissection for lymph-node metastases were performed respectively.

RESULTS

DTC recurrence was located in loco-regional lymph-nodes (n=8 patients) and in thyroid bed (n=7 patients). A total of 27 lesions was identified and injected before surgery. On a total of 124 lesions resected, histology showed 38 DTC metastases. In particular, 26 out of 27 lesions injected with [99mTc]MAA were correctly detected intra-operatively and resected without surgical complications. Ten patients received subsequent radioactive iodine (RAI) treatment to verify the complete recurrence resection. At a median follow-up of 16 months patients were classified in complete response (n=4), biochemical incomplete response (n=3), indeterminate response (n=1) with no evidence of structural disease. The remaining 7 patients were classified as structural incomplete response for cervical persistent disease (n=2), for cervical recurrence (n=2) and for both cervical and lung metastases progression (n=3).

CONCLUSIONS

ROLL is a simple and safe procedure in the surgical management of DTC loco-regional relapse.