I-PET score: Combining whole body iodine and 18 F-FDG PET/CT imaging to predict progression in structurally or biochemically incomplete thyroid cancer.

OBJECTIVE: We propose a new scoring system (I-PET) combining whole body scan (WBS) and FDG findings to identify patients who have or are likely to become refractory to radioactive iodine. DESIGN: Retrospective analysis of 142 patients age >18 with differentiated thyroid cancer who had a F-18 labelled fluoro-2-deoxyglucose (18 F-FDG) positron emission tomography (PET) and WBS within a 6-month period between 2010 and 2020. Pairs of 18 F-FDG PET and WBS were reviewed by three independent nuclear medicine physicians and an I-PET score was assigned: I-PET [0]: Iodine -ve/FDG -ve, I-PET [1]: Iodine +ve/FDG -ve, I-PET [2]: Iodine +ve/FDG +ve and I-PET [3]: Iodine -ve/FDG +ve. Patients with FDG +ve lesions (I-PET [2] and I-PET [3]) were further classified into groups A and B if SUVmax was ≤5 or >5, respectively. Follow-up data were obtained by chart review. Progression was defined as structural progression as per RECIST 1.1 or further surgical intervention; or biochemical progression as unstimulated thyroglobulin increasing >20% from baseline. RESULTS: Of 142 patients included in the study 121 patients had follow-up data available for review. At baseline, 49 patients were classified as I-PET [0], 10 as I-PET [1], 16 as I-PET [2] and 46 as I-PET [3]. Progression was seen in 11/49 (22%) of I-PET [0], 4/10 (40%) of I-PET [1], 10/16 (63%) of I-PET [2] and 34/46 (74%) of I-PET [3] (p < 0.001). I-PET [2B] and I-PET [3B] had a progression rate of 88% (7/8) and 78% (25/32), respectively. I-PET [3B] were 9.6 times more likely to commence multikinase inhibitor therapy (p = 0.001) and had 8 times greater mortality (p = 0.003) than patients in other I-PET groups combined. CONCLUSION: I-PET is a simple readily acquired imaging biomarker that potentially enhances the dynamic risk stratification and guide treatment in thyroid cancer.

A Case Report of Poor Response to Selpercatinib in the Presence of a 632_633 RET Deletion.

Background: Genomic deletions in medullary thyroid cancer (MTC) are rare. Selpercatinib is a highly selective RET inhibitor for treatment of metastatic RET-altered MTC. We report a 35-year-old male with an aggressive metastatic MTC harboring p.632_633del RET that was poorly responsive to RET kinase inhibitor selpercatinib. Objective: Our objective was to understand the clinical phenotype of p.632_633del RET in MTC in the context of novel RET kinase inhibitor treatment. Methods: Wild-type and p.632_633del RET sequences were modeled using a lighter version of the AlphaFold2 (AF2) software. Functional studies were performed on transfected HEK 293 cells (pCMV6-Entry, pCMV6-RET, or pCMV6-RET(p.632_633del) treated with inhibitors for 24 hours and analyzed on luciferase assays. Results: Structural modeling revealed a paucity of disulfide bridge between Cys630-Cys634 in p.632_633del RET sequences, apparent in wild-type, while forming an intermolecular disulfide bridge between two Cys656. Proximity of juxtamembrane segments of each dimer may impede Tyr687 phosphorylation and stable conformation of intracellular RET that hosts selpercatinib. In vitro experiments confirmed a reduction in efficacy of selpercatinib upon p.632_633del RET compared with wild-type RET control. Conclusion: Clinical presentation together with structural modeling and functional studies suggests that p.632_633del RET results in poor response to selpercatinib.

A Retrospective Cohort Study with Validation of Predictors of Differentiated Thyroid Cancer Outcomes.

Background: The goal of radioactive iodine (RAI) in differentiated thyroid cancer (DTC) is to treat metastasis and reduce recurrence risk. International guidelines provide broad risk stratification to aid treatment decisions, but a more nuanced approach to individualize care is warranted. We developed a predictive risk model for DTC. Methods: We performed a retrospective multivariable analysis of 899 patients who received RAI after thyroidectomy at a quaternary center in Australia between 2008 and 2016. Collected data included age, gender, histology, stimulated thyroglobulin (sTg), and 8th American Joint Committee Cancer (AJCC) staging. The ATA Modified Initial Risk (ATA) was calculated retrospectively. Recurrence was defined as clinically significant progression requiring either surgical intervention or administration of a second activity of RAI. Synchronous metastasis was defined as distant metastasis (i.e., outside of the neck) that was present at the time of diagnosis on structural imaging or initial post-iodine treatment scan. The features significantly associated with synchronous metastasis or recurrence were employed in the generation of a predictive risk model. A separate cohort of 393 patients who received RAI in 2017-2021 was used for validation. Results: On multivariate analysis, sTg ≥10 µg/L, extrathyroidal extension (ETE) and lymph node involvement predicted recurrence. Independent of ATA, patients with sTg ≥10 µg/L had a shorter disease-free survival (DFS) than those with sTg <10 µg/L (p < 0.001). The ETE stratified by four histological categories was significantly associated with worse DFS (p < 0.001). In a subset of patients, the presence of thyroglobulin antibody (TgAb) did not influence recurrence in patients with sTg <10 µg/L. On multivariate analysis, widespread ETE, sTg ≥10 µg/L, multifocal papillary thyroid cancer and follicular thyroid cancer were positively associated with synchronous metastasis. A predictive risk model was developed to estimate synchronous metastasis/recurrence risk and validated successfully in the second cohort. Conclusions: Our novel predictive risk model modifies and extends ATA stratification by including sTg and ETE, which we found to be independent predictors of both recurrence and synchronous metastasis in DTC.

MEN4, the MEN1 Mimicker: A Case Series of three Phenotypically Heterogenous Patients With Unique CDKN1B Mutations.

CONTEXT: Germline CDKN1B pathogenic variants result in multiple endocrine neoplasia type 4 (MEN4), an autosomal dominant hereditary tumor syndrome variably associated with primary hyperparathyroidism, pituitary adenoma, and duodenopancreatic neuroendocrine tumors. OBJECTIVE: To report the phenotype of 3 unrelated cases each with a unique germline CDKN1B variant (of which 2 are novel) and compare these cases with those described in the current literature. DESIGN/METHODS: Three case studies, including clinical presentation, germline, and tumor genetic analysis and family history. SETTING: Two tertiary University Hospitals in Sydney, New South Wales, and 1 tertiary University Hospital in Canberra, Australian Capital Territory, Australia. OUTCOME: Phenotype of the 3 cases and their kindred; molecular analysis and tumor p27kip1 immunohistochemistry. RESULTS: Family A: The proband developed multiglandular primary hyperparathyroidism, a microprolactinoma and a multifocal nonfunctioning duodenopancreatic neuroendocrine tumor. Family B: The proband was diagnosed with primary hyperparathyroidism from a single parathyroid adenoma. Family C: The proband was diagnosed with a nonfunctioning pituitary microadenoma and ectopic Cushing's syndrome from an atypical thymic carcinoid tumor. Germline sequencing in each patient identified a unique variant in CDKN1B, 2 of which are novel (c.179G > A, p.Trp60*; c.475G > A, p.Asp159Asn) and 1 previously reported (c.374_375delCT, p.Ser125*). CONCLUSIONS: Germline CDKN1B pathogenic variants cause the syndrome MEN4. The phenotype resulting from the 3 pathogenic variants described in this series highlights the heterogenous nature of this syndrome, ranging from isolated primary hyperparathyroidism to the full spectrum of endocrine manifestations. We report the first described cases of a prolactinoma and an atypical thymic carcinoid tumor in MEN4.

Change in Practice of Radioactive Iodine Administration in Differentiated Thyroid Cancer: A Single-Centre Experience.

OBJECTIVE: Our study aimed to analyse temporal trends in radioactive iodine (RAI) treatment for thyroid cancer over the past decade; to analyse key factors associated with clinical decisions in RAI dosing; and to confirm lower activities of RAI for low-risk patients were not associated with an increased risk of recurrence. METHODS: Retrospective analysis of 1,323 patients who received RAI at a quaternary centre in Australia between 2008 and 2018 was performed. Prospectively collected data included age, gender, histology, and American Joint Committee on Cancer stage (7th ed). American Thyroid Association risk was calculated retrospectively. RESULTS: The median activities of RAI administered to low-risk patients decreased from 3.85 GBq (104 mCi) in 2008-2016 to 2.0 GBq (54 mCi) in 2017-2018. The principal driver of this change was an increased use of 1 GBq (27 mCi) from 1.3% of prescriptions in 2008-2011 to 18.5% in 2017-2018. In patients assigned as low risk per ATA stratification, lower activities of 1 GBq or 2 GBq (27 mCi or 54 mCi) were not associated with an increased risk of recurrence. In patients assigned to intermediate- or high-risk categories who received RAI as adjuvant therapy, there was no difference in risk of recurrence between 4 GBq (108 mCi) and 6 GBq (162 mCi). CONCLUSIONS: Our data demonstrate an evolution of RAI activities consistent with translation of ATA guidelines into clinical practice. Use of lower RAI activities was not associated with an increase in recurrence in low-risk thyroid cancer patients. Our data also suggest lower RAI activities may be as efficacious for adjuvant therapy in intermediate- and high-risk patients.

Translational Utility of Liquid Biopsies in Thyroid Cancer Management.

Liquid biopsies are a novel technique to assess for either circulating tumor cells (CTC) or circulating tumor DNA (ctDNA and microRNA (miRNA)) in peripheral blood samples of cancer patients. The diagnostic role of liquid biopsy in oncology has expanded in recent years, particularly in lung, colorectal and breast cancer. In thyroid cancer, the role of liquid biopsy in either diagnosis or prognosis is beginning to translate from the lab to the clinic. In this review, we describe the evolution of liquid biopsies in detecting CTC, ctDNA and miRNA in thyroid cancer patients, together with its limitations and future directions in clinical practice.

ACTH-secreting medullary thyroid cancer: a case series.

Medullary thyroid cancer (MTC) is a rare neuroendocrine tumour that originates from the parafollicular cells of the thyroid gland. The most common presentation of MTC is with a single nodule; however, by the time of diagnosis, most have spread to the surrounding cervical lymph nodes. Cushing's syndrome is a rare complication of MTC and is due to ectopic adrenocorticotrophic hormone (ACTH) secretion by tumour cells. Cushing's syndrome presents a challenging diagnostic and management issue in patients with MTC. Tyrosine kinase inhibitors (TKI) previously used for the management of metastatic MTC have become an important therapeutic option for the management of ectopic ACTH in metastatic MTC. The article describes three cases of ectopic ACTH secretion in MTC and addresses the significant diagnostic and management challenges related to Cushing's syndrome in metastatic MTC. LEARNING POINTS: Medullary thyroid cancer (MTC) is a rare neuroendocrine tumour.Cushing's syndrome is a rare complication of MTC that has a significant impact on patients' morbidity and mortality.Tyrosine kinase inhibitors (TKI) provide an important therapeutic option for the management of ectopic ACTH in metastatic MTC.

The vestibular evoked-potential profile of Ménière's disease.

OBJECTIVE: To define the ocular and cervical vestibular evoked myogenic potential (oVEMP and cVEMP) profile in Ménière's Disease (MD), we studied air-conducted (AC) sound and bone-conducted vibration (BCV)-evoked responses in 77 patients and 35 controls. METHODS: oVEMPs were recorded from unrectified infra-orbital surface electromyography (EMG) during upward gaze. cVEMPs were recorded from rectified and unrectified sternocleidomastoid EMG during head elevation against gravity. Responses to AC clicks delivered via headphones and BC forehead taps delivered with a mini-shaker (bone-conduction vibrator) and a triggered tendon-hammer were recorded. RESULTS: In clinically definite unilateral MD (n=60), the prevalence of unilateral VEMP abnormalities was 50.0%, 10.2% and 11.9% for click, minitap and tendon-hammer evoked oVEMPs, 40.0%, 22.8% and 10.7% for click, minitap and tendon-hammer evoked cVEMPs. The most commonly observed profile was abnormality to AC stimulation alone (33.3%), followed by abnormalities to both AC and BCV stimuli (26.7%). Isolated abnormalities to BCV stimuli were rare (5%) and limited to the minitap cVEMP. The prevalence of abnormalities for each of the AC VEMPs was significantly higher than for any one BCV VEMP. For click cVEMP, click oVEMP and minitap cVEMP, average Reflex Asymmetry Ratios (AR) were significantly higher in MD compared with controls. Test results for AC cVEMP, AC oVEMP, minitap cVEMP and caloric asymmetry were significantly correlated with hearing loss. CONCLUSIONS: Predominance of abnormalities in oVEMP and cVEMP responses to AC sound is characteristic of MD and indicative of saccular involvement. SIGNIFICANCE: This pattern of VEMP abnormalities may enable separation of Ménière's disease from other peripheral vestibulopathies.