RCAN1.4 regulates tumor cell engraftment and invasion in a thyroid cancer to lung metastasis-on-a-chip microphysiological system.

Progressive metastasis is the primary cause of cancer-related deaths. It has been recognized that many cancers are characterized by long periods of stability followed by subsequent progression. Genes termed metastasis progression suppressors (MPS) are functional gatekeepers of this process, and their loss leads to late-stage progression. Previously, we identified regulator of calcineurin 1, isoform 4 (RCAN1.4) as a functional MPS for several cancers, including thyroid cancer, a tumor type prone to metastatic dormancy. RCAN1.4 knockdown increases expression of the cancer-promoting transcription factor NFE2-like bZIP transcription factor (NFE2L3), and through this mechanism increases cancer cell proliferation and invasion inin vitroandin vivoand promotes metastatic potential to lungs in tail vein models. However, the mechanisms by which RCAN 1.4 regulates specific metastatic steps is incompletely characterized. Studies of the metastatic cascade are limited in mouse systems due to high cost and long duration. Here, we have shown the creation of a thyroid-to-lung metastasis-on-a-chip (MOC) model to address these limitations, allowing invasion analysis and quantification on a single cell level. We then deployed the platform to investigate RCAN1.4 knockdown in fluorescently tagged hTh74 and FTC236 thyroid cancer cell lines. Cells were circulated through microfluidic channels, running parallel to lung hydrogel constructs allowing tumor cell-lung tissue interactions. Similar to studies in mouse models, RCAN1.4 knockdown increased NFE2L3 expression, globally increased invasion distance into lung constructs and had cell line and clonally dependent variations on bulk metastatic burden. In line with previousin vivoobservations, RCAN1.4 knockdown had a greater impact on hTh74 metastatic propensity than FTC236. In summary, we have developed and validated a novel MOC system evaluate and quantify RCAN1.4-regulated thyroid cancer cell lung adherence and invasion. This system creates opportunities for more detailed and rapid mechanistic studies the metastatic cascade and creates opportunities for translational assay development.

mLumiOpto is a Mitochondrial-Targeted Gene Therapy for Treating Cancer.

Mitochondria are important in various aspects of cancer development and progression. Targeting mitochondria in cancer cells holds great therapeutic promise, yet current strategies to specifically and effectively destroy cancer mitochondria in vivo are limited. Here, we developed mLumiOpto, an innovative mitochondrial-targeted luminoptogenetics gene therapy designed to directly disrupt the inner mitochondrial membrane (IMM) potential and induce cancer cell death. The therapeutic approach included synthesis of a blue light-gated cationic channelrhodopsin (CoChR) in the IMM and co-expression of a blue bioluminescence-emitting nanoluciferase (NLuc) in the cytosol of the same cells. The mLumiOpto genes were selectively delivered to cancer cells in vivo by an adeno-associated virus (AAV) carrying a cancer-specific promoter or cancer-targeted monoclonal antibody-tagged exosome-associated AAV (mAb-Exo-AAV). Induction with NLuc luciferin elicited robust endogenous bioluminescence, which activated CoChR, triggering cancer cell mitochondrial depolarization and subsequent cell death. Importantly, mLumiOpto demonstrated remarkable efficacy in reducing tumor burden and killing tumor cells in glioblastoma and triple-negative breast cancer xenograft mouse models. Furthermore, the approach induced an anti-tumor immune response, increasing infiltration of dendritic cells and CD8+ T cells in the tumor microenvironment. These findings establish mLumiOpto as a promising therapeutic strategy by targeting cancer cell mitochondria in vivo.

Defining the Functional Sensitivity for the Siemens Atellica Calcitonin Assay: Insight From a Single-Center Study.

BACKGROUND: Detectable, and especially rising postthyroidectomy serum calcitonin and carcinoembryonic antigen levels, as per American Thyroid Association guidelines, indicate potential disease presence, requiring frequent calcitonin measurement or imaging for early detection of persistent or recurrent medullary thyroid carcinoma. Thus, defining the clinical cutoff value of detection of calcitonin assays relative to imaging and clinical status is crucial for patient care. This study aimed to evaluate postoperative calcitonin levels using the new Siemens Atellica assay system to determine the most appropriate levels for clinical decision-making. METHODS: A retrospective analysis was conducted using Siemens Atellica for calcitonin testing on 56 samples from 40 patients between September 27, 2022 and August 11, 2023. Only calcitonin results performed at least 3 months post-total thyroidectomy were included. Imaging studies, within 6 months of the calcitonin report, were assessed. Carcinoembryonic antigen results were also reviewed. RESULTS: Precision analysis at 2.94 and 5.24 pg/mL revealed coefficients of variation at 16.49% and 8.87%, respectively. For the evidence of post-total thyroidectomy persistent or recurrent medullary thyroid carcinoma confirmed by imaging, using a 1.89 pg/mL cutoff for calcitonin yielded 43% sensitivity and 67% specificity. Using a 5.00 pg/mL cutoff resulted in 0% sensitivity and 100% specificity. CONCLUSIONS: Our findings indicate the potential suitability of a 5 pg/mL calcitonin cutoff on the Siemens Atellica platform for evaluating tumor persistence or recurrence in post-thyroidectomy patients in our institution. However, individual laboratories should establish their own clinical cutoff value when evaluating calcitonin levels for monitoring tumor recurrence post-thyroidectomy.

Telomere-lengthening germline variants predispose to a syndromic papillary thyroid cancer subtype.

Papillary thyroid cancer (PTC) is the most common endocrine malignancy. 10% to 15% of individuals show familial clustering with three or more affected members, but the factors underlying this risk are unknown. In a group of recently studied individuals with POT1 pathogenic variants and ultra-long telomere length, PTC was the second most common solid tumor. We tested whether variants in POT1 and four other telomere-maintenance genes associated with familial cancer underlie PTC susceptibility. Among 470 individuals, we identified pathogenic or likely pathogenic variants in three genes encoding telomere-binding proteins: POT1, TINF2, and ACD. They were found in 4.5% and 1.5% of familial and unselected cases, respectively. Individuals harboring these variants had ultra-long telomere length, and 15 of 18 (83%) developed other cancers, of which melanoma, lymphoma, and sarcoma were most common. Among individuals with PTC and melanoma, 22% carried a deleterious germline variant, suggesting that a long telomere syndrome might be clinically recognizable. Successive generations had longer telomere length than their parents and, at times, developed more cancers at younger ages. Tumor sequencing identified a single oncogenic driver, BRAF p.Val600Glu, in 10 of 10 tumors studied, but no telomere-maintenance mechanism, including at the TERT promoter. These data identify a syndromic subset of PTCs with locus heterogeneity and telomere lengthening as a convergent mechanism. They suggest these germline variants lower the threshold to cancer by obviating the need for an acquired telomere-maintenance mechanism in addition to sustaining the longevity of oncogenic mutations.

An Innovative Mitochondrial-targeted Gene Therapy for Cancer Treatment.

Targeting cancer cell mitochondria holds great therapeutic promise, yet current strategies to specifically and effectively destroy cancer mitochondria in vivo are limited. Here, we introduce mLumiOpto, an innovative mitochondrial-targeted luminoptogenetics gene therapy designed to directly disrupt the inner mitochondrial membrane (IMM) potential and induce cancer cell death. We synthesize a blue light-gated channelrhodopsin (CoChR) in the IMM and co-express a blue bioluminescence-emitting Nanoluciferase (NLuc) in the cytosol of the same cells. The mLumiOpto genes are selectively delivered to cancer cells in vivo by using adeno-associated virus (AAV) carrying a cancer-specific promoter or cancer-targeted monoclonal antibody-tagged exosome-associated AAV. Induction with NLuc luciferin elicits robust endogenous bioluminescence, which activates mitochondrial CoChR, triggering cancer cell IMM permeability disruption, mitochondrial damage, and subsequent cell death. Importantly, mLumiOpto demonstrates remarkable efficacy in reducing tumor burden and killing tumor cells in glioblastoma or triple-negative breast cancer xenografted mouse models. These findings establish mLumiOpto as a novel and promising therapeutic strategy by targeting cancer cell mitochondria in vivo.

Indolent Behavior of Malignant Bethesda III Nodules Compared to Bethesda V/VI Nodules.

BACKGROUND: The Bethesda system classifies all fine-needle aspiration specimens into 1 of 6 categories. We speculated that cancers within each Bethesda category would have distinct clinical behavior. METHODS: This is a retrospective analysis of patients from a single academic medical center with a histologic diagnosis of thyroid cancer who had an initial diagnosis of Bethesda III, IV, V, or VI cytology. RESULTS: A total of 556 cases were included, with 87 cases of Bethesda III, 109 cases of IV, 120 cases of V, and 240 cases of VI. Bethesda III showed similarities with V/VI compared to IV with a predominance of papillary thyroid cancer. The interval from diagnosis to surgery was longer in Bethesda III compared to Bethesda V/VI (median 78 vs 41 days, P < .001) (Fig. 1). Yet, patients with Bethesda III had a higher probability of achieving remission (62% vs 46%, P < .03), a lower possibility of recurrence (8% vs 24%, P < .001), and a shorter interval to achieve remission (median 1218 vs 1682 days, P = .02) compared to Bethesda V/VI, which did not change after adjusting for age, sex, radioactive iodine therapy, mode of surgery, and tumor size. More than 70% of Bethesda III that later presented with recurrence had T3/T4 disease or distant metastasis. CONCLUSION: Cancers with Bethesda III cytology had a less aggressive clinical phenotype with better prognosis compared to V/VI despite histological similarities. The time to remission was shorter in Bethesda III despite a longer interval between diagnosis and surgery. The initial cytological diagnosis may guide management.

CHEK2 Founder Variants and Thyroid Cancer Risk.

Background: Germline pathogenic variants in CHEK2 are associated with a moderate increase in the lifetime risk for breast cancer. Increased risk for other cancers, including non-medullary thyroid cancer (NMTC), has also been suggested. To date, data implicating CHEK2 variants in NMTC predisposition primarily derive from studies within Poland, driven by a splice site variant (c.444 + 1G>A) that is uncommon in other populations. In contrast, the predominant CHEK2 variants in non-Polish populations are c.1100del and c.470T>C/p.I157T, representing 61.1% and 63.8%, respectively, of all CHEK2 pathogenic variants in two large U.S.-based commercial laboratory datasets. To further delineate the impact of common CHEK2 variants on thyroid cancer, we aimed to investigate the association of three CHEK2 founder variants (c.444 + 1G>A, c.1100del, and c.470T>C/p.Ile157Thr) on NMTC susceptibility in three groups of unselected NMTC patients. Methods: The presence of three CHEK2 founder variants was assessed within three groups: (1) 1544 NMTC patients (and 1593 controls) from previously published genome-wide association study (GWAS) analyses, (2) 789 NMTC patients with germline exome sequencing (Oncology Research Information Exchange Network [ORIEN] Avatar), and (3) 499 NMTC patients with germline sequence data available in The Cancer Genome Atlas (TCGA). A case-control study design was utilized with odds ratios (ORs) calculated by comparison of all three groups with the Ohio State University GWAS control group. Results: The predominant Polish variant (c.444 + 1G>A) was present in only one case. The proportion of patients with c.1100del was 0.92% in the GWAS group, 1.65% in the ORIEN Avatar group, and 0.80% in the TCGA group. The ORs (with 95% confidence intervals [CIs]) for NMTC associated with c.1100del were 1.71 (0.73-4.29), 2.64 (0.95-7.63), and 2.5 (0.63-8.46), respectively. The proportion of patients with c.470T>C/p.I157T was 0.91% in the GWAS group, 0.76% in the ORIEN Avatar group, and 0.80% in the TCGA group, respectively. The ORs (with CIs) for NMTC associated with c.470T>C/p.I157T were 1.75 (0.74-4.39), 1.52 (0.42-4.96), and 2.31 (0.58-7.90), respectively. Conclusions: Our analyses of unselected patients with NMTC suggest that CHEK2 variants c.1100del and c.470T>C/p.I157T have only a modest impact on thyroid cancer risk. These results provide important information for providers regarding the relatively low magnitude of thyroid cancer risk associated with these CHEK2 variants.

Combined Vorinostat and Chloroquine Inhibit Sodium-Iodide Symporter Endocytosis and Enhance Radionuclide Uptake In Vivo.

PURPOSE: Patients with aggressive thyroid cancer are frequently failed by the central therapy of ablative radioiodide (RAI) uptake, due to reduced plasma membrane (PM) localization of the sodium/iodide symporter (NIS). We aimed to understand how NIS is endocytosed away from the PM of human thyroid cancer cells, and whether this was druggable in vivo. EXPERIMENTAL DESIGN: Informed by analysis of endocytic gene expression in patients with aggressive thyroid cancer, we used mutagenesis, NanoBiT interaction assays, cell surface biotinylation assays, RAI uptake, and NanoBRET to understand the mechanisms of NIS endocytosis in transformed cell lines and patient-derived human primary thyroid cells. Systemic drug responses were monitored via 99mTc pertechnetate gamma counting and gene expression in BALB/c mice. RESULTS: We identified an acidic dipeptide within the NIS C-terminus that mediates binding to the σ2 subunit of the Adaptor Protein 2 (AP2) heterotetramer. We discovered that the FDA-approved drug chloroquine (CQ) modulates NIS accumulation at the PM in a functional manner that is AP2 dependent. In vivo, CQ treatment of BALB/c mice significantly enhanced thyroidal uptake of 99mTc pertechnetate in combination with the histone deacetylase (HDAC) inhibitor vorinostat/SAHA, accompanied by increased thyroidal NIS mRNA. Bioinformatic analyses validated the clinical relevance of AP2 genes with disease-free survival in RAI-treated DTC, enabling construction of an AP2 gene-related risk score classifier for predicting recurrence. CONCLUSIONS: NIS internalization is specifically druggable in vivo. Our data, therefore, provide new translatable potential for improving RAI therapy using FDA-approved drugs in patients with aggressive thyroid cancer. See related commentary by Lechner and Brent, p. 1220.

Presumed Pathogenic Germ Line and Somatic Variants in African American Thyroid Cancer.

Background: African American (AA) thyroid cancer patients have worse prognoses than European Americans (EA), which has been attributed to both health care disparities and possible genetic differences. We investigated the impact of both germ line and somatic variants on clinical outcome in a cohort of AA nonmedullary thyroid cancer (NMTC) patients who had received therapeutic intervention from cancer centers. Methods: Whole-exome sequencing was performed on DNA from available blood/normal tissues (N = 37) and paired tumor samples (N = 32) collected from 37 and 29 AA NMTC patients, respectively. Variants with Combined Annotation Depletion Dependent (CADD) score of ≥20 and VarSome Clinical classification of likely pathogenic or pathogenic were classified as presumed pathogenic germ line or somatic variants (PPGVs/PPSVs). PPGVs/PPSVs in cancer-related genes and PPGVs in cardiovascular risk genes were further investigated, and PPGVs/PPSVs associated with African (AFR) ancestry were identified. Results: Among 17 PPGVs identified in 16 cancer predisposition or known cancer-related genes, only WRN was previously known to associate with NMTC predisposition. Among PPSVs, BRAFV600E was most the prevalent and detected in 12 of the 29 (41%) tumors. Examining PPGVs/PPSVs among three patients who died from NMTC, one patient who died from papillary thyroid carcinoma/anaplastic thyroid carcinoma (PTC/ATC) led us to speculate that the PPGV ERCC4R799W may have increased the risk of PPSV TP53R273H acquisition. Among PPGVs identified in 18 cardiovascular risk genes, PPGVs in SC5NA, GYG1, CBS, CFTR, and SI are known to have causal and pathogenic implications in cardiovascular disease. Conclusion: In this cohort, most AA-NMTC patients exhibit favorable outcomes after therapeutic intervention given at cancer centers, suggesting that health care disparity is the major contributor for worse prognoses among AA-NMTC patients. Nevertheless, the clinical impact of PPGVs that might facilitate the acquisition of TP53 tumor mutations, and/or PPGVs that predispose individuals to adverse cardiovascular events, which could be exacerbated by therapy-induced cardiotoxicity, needs to be further explored. Integrated analysis of PPGV/PPSV profiles among NMTC patients with different stages of disease may help to identify NMTC patients who require close monitoring or proactive intervention.

PDPR Gene Variants Predisposing to Papillary Thyroid Cancer.

Background: Papillary thyroid cancer (PTC) is the predominant subtype of thyroid cancer (THCA), and it can cluster in families with an autosomal dominant (AD) inheritance pattern. The aim of this study was to identify novel genes and mechanisms underlying PTC susceptibility. Methods: Our previous investigation of 17 AD PTC families led us to conduct a deeper analysis on one family (Family Q) with whole-genome sequencing data from 3 PTC-affected individuals. In addition, 323 sporadic THCA cases from Avatar data and 12 familial adenomatous polyposis (FAP) individuals with secondary THCA were screened for pyruvate dehydrogenase phosphatase regulatory (PDPR) variants. CRISPR-Cas9 was used to create PDPR-deficient THCA (TPC1) and transformed normal thyroid cell lines (N-Thyori3-1) to study the metabolic consequences of PDPR loss. Results: We found truncating PDPR splice donor variants (NM_017990.4:c.361 + 1G>C) in all affected PTC Family Q members, and another PDPR splice donor variant (NM_017990.4:c.443 + 1G>C) in a sporadic PTC case. In addition, an ultra-rare missense variant was found in an FAP-PTC patient. The PDPR-deficient cells presented with elevated phosphorylation of pyruvate dehydrogenase and altered glucose metabolism, implying that PDPR plays an essential part in regulating glucose metabolism in thyroid cells. Conclusions: Our finding of novel truncating germline variants in PDPR in Family Q and additional cohorts suggests a role for PDPR loss in PTC predisposition. Also, somatic and RNA sequencing from the thyroid carcinoma (Firehouse Legacy) data showed that PDPR gene expression is much lower in THCA tumor tissue compared with matching normal tissue. Thus, PDPR appears to have a loss of function effect on THCA tumorigenesis.

A tribute to Ernest L. Mazzaferri, MD and the lasting impact that he had on thyroid cancer care ten years after his death.

This viewpoint highlights the contributions of Dr. Ernest Mazzaferri, a prominent figure in the field of thyroid cancer care, who made significant contributions to the diagnosis and treatment of this disease. Dr. Mazzaferri's first paper on thyroid cancer, published in 1977, established fundamental principles that remain fundamental to differentiated thyroid cancer management. He was an advocate of total thyroidectomy and of postoperative radioiodine therapy and contributed to improving thyroid fine needle aspiration techniques. Dr. Mazzaferri's leadership in developing guidelines for the management of thyroid cancer and thyroid nodules has been influential and widely accepted. His groundbreaking work established a systematic and data-driven approach to the diagnosis and treatment of thyroid cancer that continues to shape the field of thyroid cancer care today. This Viewpoint reflects on his lasting impact ten years after his death.

The RCAN1.4 Metastasis Suppressor Is Hypermethylated at Intron 1 in Thyroid Cancer.

Background: Regulator of calcineurin 1.4 (RCAN1.4) is a functionally downregulated metastasis progression suppressor (MPS) in thyroid cancer; however, the mechanisms for RCAN1.4 loss in thyroid cancer have not yet been reported. The RCAN1.4 promoter and gene contain several cytosine-guanine (CG)-rich regions, some of which are reported to be hypermethylated in nonthyroid tissues. We, therefore, hypothesized that RCAN1.4 downregulation in thyroid cancer was in part due to hypermethylation. Methods: Studies were performed in 5 thyroid cancer cell lines (TPC1, FTC133, BCPAP, C643, and 8505C) with different genetic drivers, and in 18 paired normal and thyroid cancer human thyroid cancer tissues. Basal RCAN1.4 messenger RNA (mRNA) and protein levels were assessed in all of the cell lines. Cell lines with lowest RCAN1.4 expression levels were treated with the DNA methyl transferase inhibitor, decitabine. Normal/tumor tissue pairs were analyzed for methylation of three CG-rich regions both by capture of methylated DNA by MBD2 protein and by methylation-specific polymerase chain reaction (MSPCR). Results: In all assessed cell lines, RCAN1.4 mRNA and protein levels increased after decitabine treatment. In silico analysis of the RCAN1.4 gene identified 3 CG-rich regions as possible methylation targets: 1 in the proximal promoter and 2 in intron 1. Hypermethylation of the intron 1 CG-rich regions was identified by both the capture method and MSPCR. In contrast, hypermethylation of the CG-rich region of the proximal promoter was not identified. Gene expression confirmed that hypermethylation in thyroid cancer samples in intron 1 of RCAN1.4 was associated with lower levels of RCAN1.4 mRNA. Finally, the cancer samples demonstrated increased NFE2L3 expression, a downstream marker of functional RCAN1.4 loss. Conclusions: The MPS gene, RCAN1.4, is downregulated in thyroid cancer cells and human thyroid cancer in part by hypermethylation of CG-rich regions in intron 1.

Molecular testing in thyroid cancer diagnosis and management.

Molecular diagnostic testing has had a profound impact on the diagnosis and management of thyroid nodules and thyroid cancer. Based on the tremendous expansion of knowledge of the genomic landscape of thyroid cancer over the past few decades, tests have been developed, analyzed, modified, and implemented into clinical practice. Genomic testing of thyroid nodules to improve preoperative diagnosis has become an important component supporting decision-making in clinical care, reducing the need for diagnostic surgeries and improving accuracy of cancer risk assessment. In addition, a role for molecular testing of established thyroid cancers to assist in selection of therapeutic options for patients with advanced and/or progressive disease has been established. Research is ongoing to determine if molecular results should affect management of less aggressive forms of thyroid cancer earlier in clinical management. This review will outline the various commercial platforms for molecular diagnostics for nodules emphasizing their performance parameters and indications for use, as well as discuss the use of genomic analysis for progressive thyroid cancer and highlight opportunities for further research.

Adrenal Near-Infrared Autofluorescence.

Context: Parathyroid tissue is one of the few tissues to have strong near-infrared (NIR) autofluorescence, which has been exploited to improve intraoperative parathyroid identification. The US Food and Drug Administration has approved 2 devices for this purpose. Adrenal glands can be difficult to distinguish from surrounding fat, an issue during total adrenalectomy. Objective: We hypothesized adrenal tissue may also possess considerable NIR autofluorescence. Methods: Resected patient adrenal specimens were examined after robotic adrenalectomy with an NIR camera intraoperatively. Patients did not receive fluorescent dye. Images were taken of both gross and sectioned specimens. Post hoc image analysis was performed with ImageJ software. Confocal microscopy was performed on selected tissues using immunofluorescence and hematoxylin-eosin staining. Results: Resected tissue was examined from 22 patients undergoing surgery for pheochromocytomas (6), primary aldosteronism (3), adrenocorticotropin-independent hypercortisolism (10), and a growing or suspicious mass (3). Normal adrenal tissue demonstrated strong NIR autofluorescence. The intensity ratio compared to background (set as 1) for gross images was 2.03 ±â€…0.51 (P < .0001) compared to adjacent adipose of 1.24 ±â€…0.18. Autofluorescence from adrenal tumors was also detected at variable levels of intensity. Cortisol-producing tumors had the highest fluorescence ratio of 3.01 ±â€…0.41. Confocal imaging localized autofluorescence to the cytosol, with the highest intensity in the zona reticularis followed by the zona fasciculata. Conclusion: Normal and abnormal adrenal tissues possess natural NIR autofluorescence. Highest autofluorescence levels were associated with cortisol-producing tumors. Confocal imaging demonstrated the highest intensity in the zona reticularis. NIR cameras may have the potential to improve identification of adrenal tissue during surgery.

Dabrafenib Versus Dabrafenib + Trametinib in BRAF-Mutated Radioactive Iodine Refractory Differentiated Thyroid Cancer: Results of a Randomized, Phase 2, Open-Label Multicenter Trial.

Background: Oncogenic BRAF mutations are commonly found in advanced differentiated thyroid cancer (DTC), and reports have shown efficacy of BRAF inhibitors in these tumors. We investigated the difference in response between dabrafenib monotherapy and dabrafenib + trametinib therapy in patients with BRAF-mutated radioactive iodine refractory DTC. Methods: In this open-label randomized phase 2 multicenter trial, patients aged ≥18 years with BRAF-mutated radioactive iodine refractory DTC with progressive disease by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 within 13 months before enrollment were eligible. Patients were randomly assigned to receive dabrafenib alone or dabrafenib + trametinib. The primary endpoint was objective response rate by modified RECIST (minor response of -20% to -29%, partial and complete response) within the first 24 weeks of therapy. Trial Registration Number: NCT01723202. Results: A total of 53 patients were enrolled. The objective response rate (modified RECIST) was 42% (11/26 [95% confidence interval {CI} 23-63%]) with dabrafenib versus 48% (13/27 [CI 29-68%]) with dabrafenib + trametinib (p = 0.67). Objective response rate (RECIST 1.1) was 35% (9/26 [CI 17-56%]) with dabrafenib and 30% (8/27 [CI 14-51%]) with dabrafenib + trametinib. Most common treatment-related adverse events included skin and subcutaneous tissue disorders (17/26, 65%), fever (13/26, 50%), hyperglycemia (12/26, 46%) with dabrafenib alone and fever (16/27, 59%), nausea, chills, fatigue (14/27, 52% each) with dabrafenib + trametinib. There were no treatment-related deaths. Conclusions: Combination dabrafenib + trametinib was not superior in efficacy compared to dabrafenib monotherapy in patients with BRAF-mutated radioiodine refractory progressive DTC.

Serum Thyroglobulin Measurement Following Surgery Without Radioactive Iodine for Differentiated Thyroid Cancer: A Systematic Review.

Background: The utility of serum thyroglobulin (Tg) measurement following partial thyroidectomy or total/near-total thyroidectomy without radioactive iodine (RAI) for differentiated thyroid cancer is unclear. This systematic review examines the diagnostic accuracy of serum Tg measurement for persistent, recurrent, and/or metastatic cancer in these situations. Methods: Ovid MEDLINE, Embase, and Cochrane Central were searched in October 2021 for studies on Tg measurement following partial thyroidectomy or total/near-total thyroidectomy without or before RAI. Quality assessment was performed, and evidence was synthesized qualitatively. Results: Thirty-seven studies met inclusion criteria. Four studies (N = 561) evaluated serum Tg measurement following partial thyroidectomy, five studies (N = 751) evaluated Tg measurement following total/near-total thyroidectomy without RAI, and 28 studies (N = 7618) evaluated Tg measurement following total or near-total thyroidectomy before RAI administration. Following partial thyroidectomy, Tg measurement was not accurate for diagnosing recurrence or metastasis, or estimates were imprecise. Following total/near-total thyroidectomy without RAI, evidence was limited due to few studies with very low rates of recurrence or metastasis, but indicated that Tg levels were usually stable and low. For Tg measurements before RAI administration, diagnostic accuracy for metastatic disease or persistence varied, although sensitivity appeared high (but specificity low) at a cutoff of >1 to 2.5 ng/mL. However, applicability to patients who do not undergo RAI is uncertain because patients selected for RAI are likely to represent a higher risk group. The evidence was very low quality for all scenarios. All studies had methodological limitations, and there was variability in the Tg thresholds evaluated, patient populations, outcomes assessed, and other factors. Conclusions: Very limited evidence suggests low utility of Tg measurement for identifying recurrent or metastatic disease following partial thyroidectomy. Following total/near-total thyroidectomy, Tg levels using a cutoff of 1-2.5 ng/mL might identify patients at low risk for persistent or metastatic disease. Additional research is needed to clarify the role of Tg measurement in these settings, determine optimal Tg thresholds, and determine appropriate measurement intervals.

American Head and Neck Society Endocrine Surgery Section and International Thyroid Oncology Group consensus statement on mutational testing in thyroid cancer: Defining advanced thyroid cancer and its targeted treatment.

BACKGROUND: The development of systemic treatment options leveraging the molecular landscape of advanced thyroid cancer is a burgeoning field. This is a multidisciplinary evidence-based statement on the definition of advanced thyroid cancer and its targeted systemic treatment. METHODS: An expert panel was assembled, a literature review was conducted, and best practice statements were developed. The modified Delphi method was applied to assess the degree of consensus for the statements developed by the author panel. RESULTS: A review of the current understanding of thyroid oncogenesis at a molecular level is presented and characteristics of advanced thyroid cancer are defined. Twenty statements in topics including the multidisciplinary management, molecular evaluation, and targeted systemic treatment of advanced thyroid cancer are provided. CONCLUSIONS: With the growth in targeted treatment options for thyroid cancer, a consensus definition of advanced disease and statements regarding the utility of molecular testing and available targeted systemic therapy is warranted.

Active Surveillance Versus Thyroid Surgery for Differentiated Thyroid Cancer: A Systematic Review.

Background: Active surveillance has been proposed as an appropriate management strategy for low-risk differentiated thyroid cancer (DTC), due to the typically favorable prognosis of this condition. This systematic review examines the benefits and harms of active surveillance vs. immediate surgery for DTC, to inform the updated American Thyroid Association guidelines. Methods: A search on Ovid MEDLINE, Embase, and Cochrane Central was conducted in July 2021 for studies on active surveillance vs. immediate surgery. Studies of surgery vs. no surgery for DTC were assessed separately to evaluate relevance to active surveillance. Quality assessment was performed, and evidence was synthesized narratively. Results: Seven studies (five cohort studies [N = 5432] and two cross-sectional studies [N = 538]) of active surveillance vs. immediate surgery, and seven uncontrolled treatment series of active surveillance (N = 1219) were included. One cross-sectional study was rated fair quality, and the remainder were rated poor quality. In patients with low risk (primarily papillary), small (primarily ≤1 cm) DTC, active surveillance, and immediate surgery were associated with similar, low risk of all-cause or cancer-specific mortality, distant metastasis, and recurrence after surgery. Uncontrolled treatment series reported no cases of mortality in low-risk DTC managed with active surveillance. Among patients managed with active surveillance, rates of tumor growth were low; rates of subsequent surgery varied and primarily occurred due to patient preference rather than tumor progression. Four cohort studies (N = 88,654) found that surgery associated with improved all-cause or thyroid cancer mortality compared with nonsurgical management, but findings were potentially influenced by patient age and tumor risk category and highly susceptible to confounding by indication; eligibility for, and receipt of, active surveillance; and timing of surgery was unclear. Conclusions: In patients with small low-risk (primarily papillary) DTC, active surveillance and immediate surgery may be associated with similar mortality, risk of recurrence, and other outcomes, but methodological limitations preclude strong conclusions. Studies of no surgery vs. surgery are difficult to interpret due to clinical heterogeneity and potential confounding factors and are unsuitable for assessing the utility of active surveillance. Research is needed to clarify the benefits and harms of active surveillance and determine outcomes in nonpapillary DTC, larger (>1 cm) cancers, and older patients.

RAC1 Alterations Induce Acquired Dabrafenib Resistance in Association with Anaplastic Transformation in a Papillary Thyroid Cancer Patient.

BRAF-activating mutations are the most frequent driver mutations in papillary thyroid cancer (PTC). Targeted inhibitors such as dabrafenib have been used in advanced BRAF-mutated PTC; however, acquired resistance to the drug is common and little is known about other effectors that may play integral roles in this resistance. In addition, the induction of PTC dedifferentiation into highly aggressive KRAS-driven anaplastic thyroid cancer (ATC) has been reported. We detected a novel RAC1 (P34R) mutation acquired during dabrafenib treatment in a progressive metastatic lesion with ATC phenotype. To identify a potential functional link between this novel mutation and tumor dedifferentiation, we developed a cell line derived from the metastatic lesion and compared its behavior to isogenic cell lines and primary tumor samples. Our data demonstrated that RAC1 mutations induce changes in cell morphology, reorganization of F-actin almost exclusively at the cell cortex, and changes in cell adhesion properties. We also established that RAC1 amplification, with or without mutation, is sufficient to drive cell proliferation and resistance to BRAF inhibition. Further, we identified polyploidy of chromosome 7, which harbors RAC1, in both the metastatic lesion and its derived cell line. Copy number amplification and overexpression of other genes located on this chromosome, such as TWIST1, EGFR, and MET were also detected, which might also lead to dabrafenib resistance. Our study suggests that polyploidy leading to increased expression of specific genes, particularly those located on chromosome 7, should be considered when analyzing aggressive thyroid tumor samples and in further treatments.