Medullary Thyroid Carcinoma Research Articles

Endocrine Perspective of Cutaneous Lichen Amyloidosis: RET-C634 Pathogenic Variant in Multiple Endocrine Neoplasia Type 2

Background: Medullary thyroid carcinoma (MTC), the third most frequent histological type of thyroid malignancy, may be found isolated or as part of multiple endocrine neoplasia type 2 (MEN2). One particular subtype of this autosomal dominant-transmitted syndrome includes an association with cutaneous lichen amyloidosis, although, generally, a tide genotype–phenotype correlation is described in patients who carry RET proto-oncogene pathogenic variants. Methods: Our objective was to provide an endocrine perspective of a case series diagnosed with RET-positive familial MTC associated with cutaneous primary lichen amyloidosis amid the confirmation of MEN2. Six members of the same family had cutaneous lesion with different features (from hyperpigmented, velvety to red/pink appearance) and four of them harbored a RET pathogenic variant at 634 codon (exon 11): c.1900T>G, p.634G (TGC634CGC). Results: All six patients were females with the lesion at the interscapular region. Except for two women, four of these subjects were investigated and had MTC (three of them with postoperatory confirmation). The youngest affected individual was 6 years old. The three adult females were confirmed with RET pathogenic variant during their 30s, while the girl underwent the familial screening as a newborn. None of them had primary hyperparathyroidism until the present time, except for one subject, and two out of the three adults also had bilateral pheochromocytoma. Notably, all patients were rather asymptomatic from the endocrine perspective at the moment when endocrine tumor/cancer was confirmed, and the skin was progressively affected a few years before the actual MEN2 confirmation. Conclusions: This case series highlights the following key message: awareness of the dermatologic findings in MTC/MEN2 patients is essential since lesions such as cutaneous lichen amyloidosis might represent the skin signature of the endocrine condition even before the actual endocrine manifestations. These data add to the limited published reports with respect to this particular presentation, noting the fact that RET-C634 is the most frequent pathogenic variant in MEN2-associated lichen amyloidosis; females are more often affected; the interscapular region is the preferred site; the age of diagnosis might be within the third decade of life, while we reported one of the youngest patients with the lesion. The same RET pathogenic variant is not associated with the same dermatologic features as shown in the vignette. The same RET mutation does not mean that all family members will present the same skin anomaly.

CTR-FAPI PET enables precision management of medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC) can only be cured through the excision of all metastatic lesions, but 29-60% patients failed to localize the disease in the current clinical practice. Previously, we developed a fibroblast activation protein inhibitor (FAPI)-based covalent targeted radioligand (CTR) for improved detection sensitivity and accuracy. In this first-in-class clinical trial, we head-to-head compared [68Ga]Ga-CTR-FAPI PET-CT and [18F]FDG PET-CT in 50 MTC patients. The primary endpoint was the patient-based detection rate, with [68Ga]Ga-CTR-FAPI exhibiting higher detection than [18F]FDG (98% vs. 66%, p=0.0002). This improved detection was attributed to increased tumor uptake (SUVmax 11.71±9.16 vs. 2.55±1.73, p<0.0001). Diagnostic accuracy, validated on lesions with gold-standard pathology, was greater for [68Ga]Ga-CTR-FAPI compared to [18F]FDG (96.7% vs. 43.3%, p<0.0001). Notably, 32% patients altered management following [68Ga]Ga-CTR-FAPI PET-CT, and 66.7% patients changed their surgical plan. Overall, [68Ga]Ga-CTR-FAPI PET-CT provided superior detection and diagnostic accuracy compared to [18F]FDG PET-CT, enabling precision management of MTC patients.

PD-L1 Expression Varies in Thyroid Cancer Types and Is Associated with Decreased Progression Free Survival (PFS) in Patients with Anaplastic Thyroid Cancer

Background: Thyroid cancer (TC) remains a significant clinical challenge worldwide, with a subset of patients facing aggressive disease progression and therapeutic resistance. Immune checkpoint inhibitors targeting programmed death-ligand 1 (PD-L1) have emerged as promising therapeutic approaches for various malignancies, yet their efficacy in TC remains uncertain. The objective of this study was to investigate PD-L1 expression in aggressive TC and its association with histological subtypes, molecular mutation, and progression-free survival. Methods: This is a retrospective study of patients with advanced TC seen in two tertiary health care centers. Included in this study were patients with advanced TC with recurrence or progression on therapy for whom tumor molecular profiling and PD-L1 status were available. Kaplan–Meier estimators were utilized to analyze the progression-free survival (PFS) between patients with PD-L1 positive and negative status in Anaplastic TC (ATC) subgroup. Results: A total of 176 patients with advanced thyroid cancer were included (48.9% female). Of the patients, 13 had ATC, 11 Medullary TC (MTC), 81 Papillary TC Classic Variant (PTCCV), 20 Follicular TC (FTC), 8 Oncocytic TC (OTC), 10 Poorly Differentiated TC (PDTC), and 30 had the Papillary TC Follicular Variant (PTCFV). BRAF mutation was present in 41%, TERT in 30%, RAS in 19%, TP53 in 10%, and RET in 8.6% of patients. PD-L1 positivity was significantly different across different TC types and histological subtypes (p &lt; 0.01): Patients with OTC had the highest frequency of PD-L1 positivity (71%), followed by ATC (69%), PTCCV (28.5%), and FTC (11%). Patients with MTC and PTCFV did not exhibit any PD-L1 positivity. TP53 mutation was positively associated with PD-L1 expression (21.6% vs. 7.5%, p = 0.03), and RAS mutation was negatively associated with PD-L1 expression (8.1% vs. 24.2% p = 0.04). Among patients with ATC, positive PD-L1 expression was associated with lower PFS (p = 0.002). Conclusions: PD-L1 expression varies across different TC types and histological subtypes and may be modulated by the mutational landscape. PD-L1 expression in ATC is associated with shorter PFS. Follow up studies are warranted to elucidate the molecular mechanism driving the observed differences in immune pathways, potentially paving the way for the development of more effective and personalized immune therapies for patients with aggressive TC.

Rare Combination of Multiple Endocrine Neoplasia 1 with Medullary Thyroid Carcinoma and Clinical Value of 68Ga-DOTATATE PET/CT in Diagnosing Different Lesions and Exploring Theranostic Strategy

Rare Combination of Multiple Endocrine Neoplasia 1 with Medullary Thyroid Carcinoma and Clinical Value of 68Ga-DOTATATE PET/CT in Diagnosing Different Lesions and Exploring Theranostic Strategy

Clinicopathological Characteristics of Collision tumors of Thyroid in the clinical setting of Medullary Thyroid Carcinoma.

Clinicopathological Characteristics of Collision tumors of Thyroid in the clinical setting of Medullary Thyroid Carcinoma.

Use of Glucagon-Like Peptide-1 Receptor Agonists Does Not Increase the Risk of Cancer in Patients with Type 2 Diabetes Mellitus.

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are increasingly used for the treatment of type 2 diabetes mellitus (T2DM) given their extra-pancreatic effects. However, there are concerns about carcinogenesis in the pancreas and thyroid gland. We aimed to evaluate the site-specific incidence of cancer in patients with T2DM-treated GLP-1 RAs using a nationwide cohort. This study included data obtained from the Korean National Health Insurance Service (between 2004 and 2021). The primary outcome was newly diagnosed cancer, and the median follow-up duration for all participants was 8 years. After propensity score matching, 7,827 participants were analyzed; 2,609 individuals each were included in the GLP-1 RA, diabetes mellitus (DM) control, and non-DM control groups. The incidence rate ratio (IRR) of subsequent cancer in patients with T2DM was 1.73, which was higher than that of individuals without DM, and it increased in both men and women. Analysis of patients with T2DM showed no increased cancer risk associated with the use of GLP-1 RA, and similar results were observed in both men and women. The IRRs of pancreatic cancer (0.74), thyroid cancer (1.32), and medullary thyroid cancer (0.34) did not significantly increase in the GLP-1 RA group compared with those in the DM control group. There was a 73% higher risk of cancer in patients with T2DM compared with the general population. However, among patients with T2DM, there was no association between the use of GLP-1 RAs and new-onset cancers, including pancreatic and medullary thyroid cancers.

Dual Immune Checkpoint Inhibition in Patients With Aggressive Thyroid Carcinoma

Aggressive thyroid carcinoma, including radioiodine refractory (RAIR) differentiated thyroid carcinoma (DTC), medullary thyroid carcinoma (MTC), and anaplastic thyroid carcinoma (ATC), are associated with significant morbidity and mortality and have limited therapeutic options. Distinct immune profiles have been identified in thyroid cancer subtypes suggesting they may be susceptible to immune checkpoint inhibition. To evaluate the efficacy of anti-programmed cell death 1 nivolumab and anti-cytotoxic lymphocyte-associated protein 4 ipilimumab in patients with aggressive thyroid carcinoma. This phase 2 nonrandomized clinical trial enrolled patients with RAIR DTC in a single center from October 2017 to May 2019, with exploratory cohorts in MTC and ATC. The data were analyzed between June 2021 and September 2023. Intravenous nivolumab, 3 mg/kg, every 2 weeks and ipilimumab, 1 mg/kg, every 6 weeks until disease progression, intolerable adverse events, or a maximum duration of 2 years. The primary end point of the study was objective response rate (ORR) in RAIR DTC, which was scored according to RECIST (Response Evaluation Criteria in Solid Tumours), version 1.1. Key secondary end points included safety, progression-free survival, overall survival, and biomarker analyses. A total of 51 patients were registered, and 49 patients were evaluable for analysis. The median (range) age was 65 years (30-88 years), and 25 participants (51%) were female. ORR in the DTC cohort was 9.4% (3/32 [95% CI, 2.8%-28.5%]), with all partial responses in either oncocytic carcinoma (2/6 [33.0%]) or poorly differentiated thyroid carcinoma (1/5 [20.0%]). Clinical benefit rates were 62.5% (20/32) in the overall DTC cohort, including 83.3% (5/6) in oncocytic carcinoma and 40% (2/5) in poorly differentiated thyroid carcinoma. ORR in the exploratory ATC cohort was 30.0% (3/10 [95% CI, 6.7%-65.2%]), with a clinical benefit rates of 50.0% (5/10). No responses were observed in the exploratory MTC cohort. The safety profile was similar to prior reports with dual immune checkpoint inhibition (pruritus, rash, diarrhea, fatigue, and elevation of lipase and liver enzymes). The presence of NRAS tumor genetic sequence variations, but not BRAF V600E, was associated with worse outcomes. This phase 2 nonrandomized clinical trial reported clinical activity of dual immune checkpoint inhibition in aggressive thyroid cancer. The study did not meet its end point in the primary population of RAIR DTC and does not support further investigation in non-biomarker-selected DTC. However, the signal observed in ATC may merit further evaluation. ClinicalTrials.gov Identifier: NCT03246958.

FAM20C Promotes Papillary Thyroid Cancer Proliferation and Metastasis via Epithelial-Mesenchymal Transition.

Thyroid cancer (TC) is the prevailing malignancy that impacts the endocrine system, accounting for 1% of all recently diagnosed malignancies in humans. The incidence of TC has been continuously increasing, which can be attributed to advancements in clinical diagnostic technology. However, the mechanisms behind the development of TC are still not well understood. TC is classified into four pathological forms: medullary thyroid cancer, papillary thyroid cancer (PTC), follicular thyroid cancer, and poorly differentiated TC. PTC constitutes more than 80% of all TC cases globally. Current research indicates that complex genetic and cellular processes could be responsible for the growth and spread of TC. Next-generation sequencing (RNA-seq) of 79 PTC samples and their corresponding normal thyroid tissues was performed to investigate the molecular mechanisms of PTC. An analysis of RNA-seq data from a local cohort from The Cancer Genome Atlas (TCGA) revealed that, compared with normal tissues, PTC tissues presented elevated FAM20C expression levels. In vitro, the function of FAM20C was validated with small interfering RNA (siRNA). Gene set enrichment analysis (GSEA) revealed the pathways influenced by FAM20C. A western blot experiment was used to investigate protein expression levels associated with epithelial‒mesenchymal transition (EMT). In conclusion, by regulating EMT, FAM20C facilitates PTC cell proliferation and metastasis.

High Expression of Immune Checkpoint Molecules in Different Types of Thyroid Cancer

This study aimed to investigate the expression of programmed cell death protein-1 (PD-1) and its ligand (PD-L1) immune checkpoint molecules in thyroid carcinomas and determine their association with the clinicopathological characteristics of patients. Thyroid tissue specimens from 100 patients diagnosed with primary thyroid carcinomas including papillary thyroid carcinoma (PTC), follicular thyroid carcinoma (FTC), medullary thyroid carcinoma (MTC), and anaplastic thyroid carcinoma (ATC) were collected. Sections were prepared from formalin-fixed paraffin-embedded samples, and PD-1 and PD-L1 expressions were examined using immunohistochemistry. PD-1 was detected in tumor-infiltrating lymphocytes (TILs) in 88% of the patients and tumor cells in 28% of the patients with 10% in PTC, 5% in FTC, 5% in MTC, and 8% in ATC). PD-L1 was found in tumor cells and TILs in 30% and 79% of the patients, respectively. Moreover, a significant difference was observed in PD-1 and PD-L1 expression between tumor cells and TILs across different tumor types. However, their expression in tumor cells and TILs was significantly higher in ATC compared to other tumor types. Additionally, the expression of PD-1 and PD-L1 was significantly associated with an advanced stage, higher tumor size, tumor necrosis, and mitosis. A significant positive correlation was also observed between the expression of PD-1 and PD-L1 in tumor cells and TILs. The higher expression of PD-1 and PD-L1 may contribute to tumor progression. Therefore, combinational immunotherapy by these immune checkpoint inhibitors might be a promising strategy for clinical improvement in patients with thyroid cancer, especially those with ATC.

Tumor Volume Doubling Time of Less Than One Year is Associated with a Higher Risk of Death from Medullary Thyroid Cancer.

Tumor volume doubling time (TVDT) is emerging as a useful tool in predicting oncologic outcomes. There is limited data on the prognostic role of TVDT in metastatic medullary thyroid cancer (MTC). The goal of this study was to assess the value of TVDT in predicting disease-specific survival (DSS) in patients with hereditary and sporadic MTC. This was an Institutional Review Board-approved cohort study including patients with metastatic MTC having at least 3 consecutive imaging studies. TVDT of up to the five largest lesions per organ was calculated using a standardized formula. The association between TVDT and DSS was analyzed using Kaplan-Meier survival curves. Cox proportional regression model was used to account for confounding factors. The study sample consisted of 51 patients presenting with 286 metastatic lesions measured with 457 scans during the follow-up of 51 (IQR 25-102) months. Median age was 19 years (IQR 15-41), 53% female patients. Cumulative volumes of all metastatic lesions and proportion of patients with TVDT of <1 year were higher in patients with sporadic as compared with hereditary MTC (p<0.01). Factors independently associated with shorter DSS were TVDT of <1 year based on 3 initial and 3 last scans as well as lung, brain and prostate as the organs with the fastest growing tumor. TVDT based on 2-dimentional and 3-dimentional measurements showed strong correlation (r=0.94, p<0.05). Three baseline and three most recent scans preceding follow-up visit enable calculation of TVDT and can be used as predictors of mortality from MTC.

Coexisting Medullary and Papillary Thyroid Carcinomas: A Case of Dual Neoplasia With a High Risk of Misdiagnosis

Coexisting Medullary and Papillary Thyroid Carcinomas: A Case of Dual Neoplasia With a High Risk of Misdiagnosis

PET/CT imaging of differentiated and medullary thyroid carcinoma using the novel SSTR-targeting peptide [18F]SiTATE - first clinical experiences.

The novel 18F-labeled somatostatin receptor (SSTR)-directed radiotracer [18F]SiTATE demonstrated promising results for the imaging of various SSTR-expressing tumor types. Although thyroid carcinomas (TC) express SSTR, data on [18F]SiTATE PET/CT imaging in TC are lacking. This study explores the use of [18F]SiTATE PET/CT in a patient cohort with histologically proven TC. As part of a prospective observational study at a single tertiary cancer center, 21 patients with TC (10 medullary (MTC) and 11 differentiated (DTC)) who underwent at least one [18F]SiTATE PET/CT were included (37 scans in total). Mean SUVmax and SUVmean of tumoral lesions, mean total-tumor-volume (TTV), and whole-body (WB)-SUVmax and WB-SUVmean on PET with their standard deviations (SDs) were determined. PET parameters were correlated to clinical parameters including tumor marker levels (thyroglobulin for DTC, calcitonin for MTC). 89 lesions were included in the analysis. Metastases were localized in the bone, lymph nodes, lung, soft tissue, and thyroid bed. Osseous (31 lesions; SUVmax 8.6 ± 8.0; SUVmean 5.8 ± 5.4) and nodal (37 lesions; SUVmax 8.7 ± 7.8; SUVmean 5.7 ± 5.4) metastases showed the highest uptake. The MTC disease burden on PET significantly correlated with the calcitonin tumor marker level (e.g., TTV: r = 0.771, r2 = 0.594, p = 0.002). For DTC, no such correlation was present. Our data demonstrate high feasibility of [18F]SiTATE PET/CT in a small cohort of patients with MTC and DTC. The use of [18F]SiTATE may overcome logistical disadvantages of 68Ga-based tracers and facilitate SSTR-targeted PET/CT imaging of thyroid carcinoma.

Approach to the patient with thyroid nodules: considering GLP-1 receptor agonists.

Glucagon-like peptide 1 receptor agonists (GLP1RA) have rapidly changed the landscape of diabetes and obesity treatment. Enthusiasm for their use is tempered with concerns regarding their risk for inducing C-cell tumors based on preclinical studies in rodents. A black-box warning from the United States Food and Drug Administration (USFDA) recommends against using GLP1RA in patients with a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2A or 2B (MEN2), providing clear guidance regarding this cohort of patients. However, emerging data also suggest an increased incidence of differentiated thyroid cancer (DTC) in patients treated with these agents. Other studies, though, have not confirmed an association between GLP1RA and DTC. With conflicting results concerning thyroid cancer risk, there is no clear consensus regarding the optimal approach to screening patients prior to initiating the medications and/or evaluating for thyroid cancer during GLP1RA treatment. Within the context of patient cases, this review will summarize the existing data, describe ongoing controversies, and outline future areas for research regarding thyroid cancer risk with GLP1RA use.

Holomics and Artificial Intelligence-Driven Precision Oncology for Medullary Thyroid Carcinoma: Addressing Challenges of a Rare and Aggressive Disease.

Background/Objective: Medullary thyroid carcinoma (MTC) is a rare yet aggressive form of thyroid cancer comprising a disproportionate share of thyroid cancer-related mortalities, despite its low prevalence. MTC differs from other differentiated thyroid malignancies due to its heterogeneous nature, presenting complexities in both hereditary and sporadic cases. Traditional management guidelines, which are designed primarily for papillary thyroid carcinoma (PTC), fall short in providing the individualized care required for patients with MTC. In recent years, the sheer volume of data generated from clinical evaluations, radiological imaging, pathological assessments, genetic mutations, and immunological profiles has made it humanly impossible for clinicians to simultaneously analyze and integrate these diverse data streams effectively. This data deluge necessitates the adoption of advanced technologies to assist in decision-making processes. Holomics, which is an integrated approach that combines various omics technologies, along with artificial intelligence (AI), emerges as a powerful solution to address these challenges. Methods: This article reviews how AI-driven precision oncology can enhance the diagnostic workup, staging, risk stratification, management, and follow-up care of patients with MTC by processing vast amounts of complex data quickly and accurately. Articles published in English language and indexed in Pubmed were searched. Results: AI algorithms can identify patterns and correlations that may not be apparent to human clinicians, thereby improving the precision of personalized treatment plans. Moreover, the implementation of AI in the management of MTC enables the collation and synthesis of clinical experiences from across the globe, facilitating a more comprehensive understanding of the disease and its treatment outcomes. Conclusions: The integration of holomics and AI in the management of patients with MTC represents a significant advancement in precision oncology. This innovative approach not only addresses the complexities of a rare and aggressive disease but also paves the way for global collaboration and equitable healthcare solutions, ultimately transforming the landscape of treatment and care of patients with MTC. By leveraging AI and holomics, we can strive toward making personalized healthcare accessible to every individual, regardless of their economic status, thereby improving overall survival rates and quality of life for MTC patients worldwide. This global approach aligns with the United Nations Sustainable Development Goal 3, which aims to ensure healthy lives and promote well-being at all ages.

Unveiling new chapters in medullary thyroid carcinoma therapy: advances in molecular genetics and targeted treatment strategies.

Medullary Thyroid Carcinoma (MTC), a neuroendocrine malignancy that arises from the calcitonin-secreting parafollicular C-cells of the thyroid, constitutes a minor yet impactful fraction of thyroid malignancies. Distinguished by its propensity for aggressive growth and a pronounced tendency for metastasis, MTC poses formidable obstacles to the early diagnosis and therapeutic intervention. The molecular genetics of MTC, particularly the role of the RET gene and the RAS gene family, have been extensively studied, offering insights into the pathogenesis of the disease and revealing potential therapeutic targets. This comprehensive review synthesizes the latest advancements in the molecular genetics of MTC, the evolution of precision therapies, and the identification of novel biomarkers. We also discuss the implications of these findings for clinical practice and the future direction of MTC research.

6454 Identifying Gaps in Obtaining Germline RET Testing for Patients with Medullary Thyroid Cancer

Abstract Disclosure: A.N. Lim: None. J. Comeaux: None. C. Ricker: None. K.S. Wei: None. T.E. Angell: None. Background: Medullary thyroid carcinoma (MTC) occurs sporadically or from germline pathogenic variants of the RET proto-oncogene in multiple endocrine neoplasia type 2 (MEN2). Current ATA guidelines recommend germline RET testing in all patients with C-cell hyperplasia or MTC. Because disparities may exist in the implementation of this recommendation, we analyzed records of patients with MTC to identify variables associated with germline RET testing. Methods: Patients with MTC were identified from a cohort study of all adult patients undergoing thyroid surgery from 2015-2022 at two affiliated academic centers: a private hospital or a safety-net hospital. Patients were categorized as RET-tested or not RET-tested. Data collection included: patient age, gender, ethnicity, nodule and lymph nodule findings on ultrasound (US), calcitonin and CEA levels, and surgical pathology results. Medical reports were reviewed for reasons that RET testing was or was not obtained. Results: Of 24 MTC patients, 50% were female, mean age ± SD was 50.8 ± 12.3, and 15 (62.5%) had Hispanic ethnicity. RET testing was performed in 14 (58.3%) patients and 3 (21.4%) had a pathogenic variant. RET-tested patients had a median nodule size of 3.45 cm (IQR 2.40-4.53) vs. 2.40 cm (IQR 0.98-3.25) in not-RET tested patients (p&amp;lt;0.05). There were no significant differences between groups in age, gender, ethnicity, preoperative US findings, preoperative calcitonin or CEA levels, or histopathologic status. RET testing was performed in 11/14 (78.6%) patients at the private hospital vs. only 5/10 (50.0%) patients at the safety-net hospital (p=0.20). Considering this, we further investigated the use of RET testing in the initial management of MTC patients. RET testing was performed or planned during initial management in 13/14 (92.9%) patients at the private hospital vs. only 5/10 (50%) patients at the safety-net hospital (p=0.05). At the private hospital, RET testing was requested for apparent sporadic disease (n=11), family history of MTC (n=1), and coexistent pheochromocytoma (n=1). At the safety-net hospital, RET testing was requested for apparent sporadic disease (n=4) and family history of MTC (n=1), but reportedly was not pursued in 5 patients because MTC appeared to be sporadic. Discussion: In this cohort of patients with MTC, larger nodule size was significantly associated with the rate of germline RET testing. Larger MTC tumor size alone may have prompted greater attention to germline testing, but also may have been associated with other findings, which could be further assessed with a larger sample size by multivariable analysis. The disparity in RET testing as part of initial management at the safety-net hospital may be multifactorial, but future analyses should explore provider decision-making, as well as facility and patient variables. Presentation: 6/1/2024

12396 A Case Of Medullary Thyroid Carcinoma Without Germline RET Mutation

Abstract Disclosure: I. Marranzini Rodriguez: None. M. Lemelman: None. L. Canham: None. Background: Medullary thyroid cancer (MTC) is a neuroendocrine tumor that originates from the parafollicular C cells of the thyroid gland. MTC accounts for approximately 5% of thyroid cancer in children, and the majority of MTC cases are associated with the autosomal dominant tumor predisposition syndrome Multiple Endocrine Neoplasia 2 (MEN2). Sporadic MTC is uncommon in the pediatric population and associated with somatic mutations of RET or RAS (1). Existing management options for metastatic disease have demonstrated some benefit, however, with systemic side effects. Selpercatinib, a highly selective RET kinase inhibitor, is FDA approved for patients &amp;gt;= 12 years of age. Here we present a case of a 10-year-old patient with metastatic MTC with encouraging results. Clinical Case: A previously healthy 10 year 2-month-old male presented with left-sided neck swelling. Imaging showed a 9.7 cm solid mass spanning nearly the entire left neck, occluding the left internal jugular vein, extending to the upper chest, and resulting in high-grade narrowing of the trachea near the thoracic inlet; the mass involved the left thyroid gland and engulfed the left common carotid. His initial lab evaluation showed an elevated TSH of 10.10 mcU/mL (0.6-5.5 mcU/mL) and Free T4 1.22 ng/dL (0.9-1.67 ng/dL). Tumor markers revealed a calcitonin of 32,264 pg/mL (normal range &amp;lt;= 6.0 pg/mL) and carcinoembryonic antigen (CEA) of 200 ng/ml (normal range 0 – 3.4 ng/mL). He underwent biopsy of the mass which showed medullary thyroid carcinoma (MTC) and genetic evaluation of tumoral tissue showed RET c.2753T&amp;gt;C, p.M918T somatic mutation. Evaluation for pheochromocytoma and hyperparathyroidism, given association of MTC with MEN2, was negative. Genetic testing was negative for germline RET mutations. He was started on selpercatinib, 120 mg every 12 hours. Follow up imaging after 2 months of therapy demonstrated a significant decrease in tumor burden. Approximately 5 months after starting he had a decrease in CEA to 14.8 ng/mL and calcitonin to 69 pg/mL, prior to surgery. Given the risk of locoregional recurrence he underwent total thyroidectomy with lateral neck dissection. However, the tumor was noted to be adherent to the trachea, encasing the left recurrent laryngeal nerve, and left carotid artery preventing full resection. He was started on levothyroxine at 62.5 mcg daily on POD#1 and re-started on selpercatinib approximately 2 weeks post-operatively. Conclusion: We present a case of RET-positive metastatic medullary thyroid carcinoma without germline RET mutation successfully treated with selpercatinib. Long-term follow-up for sustained response and tolerability is needed. Reference: 1. Bauer, Andrew J. “Pediatric Thyroid Cancer: Genetics, Therapeutics and Outcome.” Endocrinology and metabolism clinics of North America vol. 49,4 (2020): 589-611. doi:10.1016/j.ecl.2020.08.00 Presentation: 6/2/2024

12556 Medullary Thyroid Cancer With Persistent Elevation Of Carcinoembryonic Antigen: Case Report

Abstract Disclosure: M.S. Campana: None. Introduction: Medullary thyroid Cancer (MTC) is a rare neuroendocrine tumor that originates from thyroid parafollicular C-cells and represents 5 % of all thyroid cancers. MTC can be sporadic (75%) or hereditary (25%) associated with multiple endocrine neoplasia type 2 syndrome (MEN2). Serum calcitonin (Ctn) and carcinoembryonic antigen (CEA) are its tumor markers. We report a case of persistently elevated CEA levels despite an undetectable Ctn in a patient with MTC after initial thyroid lobectomy. Description of the case: A 42-year-old woman self-identified a neck lump after intentional weight loss. A neck US showed a right lobe thyroid nodule which resulted as suspicious for malignancy (Bethesda V) with subsequent right lobectomy. Pathology reported a 2.6 cm unexpected MTC with negative surgical margins, extrathyroidal extension, angioinvasion, and lymphatic invasion. No cervical lymph nodes (LNs) were removed. Immunohistochemistry was positive for CEA, chromogranin A, synaptophysin, and Ctn. T2 Nx. One month after lobectomy, the Ctn was 10.5 (0-3.0 pg/mL) and CEA 205.2 (0-3.0 ng/mL Non-smoker; 0-5.0 ng/mL smoker). The patient was then referred to our clinic for further management. Laboratories showed normal serum calcium, PTH, and fractionated plasma metanephrine/normetanephrine. A 2-month post-operative Ctn was undetectable, but CEA was elevated at 24.5. Subsequently, we broaden imaging studies to include neck US, CT neck /chest with contrast, and MRI abdomen pelvis with contrast. The only remarkable finding was a 6.7 cm pelvic mass with normal Ca-125. Genetic testing was negative for germline RET, ruling out MEN2. Patient underwent completion left lobectomy with prophylactic bilateral central neck dissection. Pathology showed benign thyroid parenchyma with multinodular hyperplasia and 0/12 LNs. Because of concerning pelvic mass, the patient was referred to OB/GYN. She underwent a laparoscopic bilateral salpingo-oophorectomy. Pathology showed a follicular ovarian cyst, negative for malignancy. A year post-completion total thyroidectomy Ctn remains undetectable, and a CEA is normal at 1.3. Discussion: Because Ctn was already undetectable 1 month after lobectomy with persistent elevated CEA a complete total thyroidectomy with prophylactic bilateral central neck dissection was indicated to achieve operative cure. Ctn is specific to MTC but variable. CEA is more reproducible with less variability; however, it is not specific to MTC and can also be elevated in smokers, benign breast and genitourinary disease, emphysema, cirrhosis, and cancer of colon, rectum, liver, genitourinary, and lung. If residual disease is present, Ctn tends to be proportionally more elevated than CEA. When the opposite occurs, poorly differentiated MTC with possibility of distant metastases vs. a second primary malignancy vs. a distant benign neoplasm known to elevate CEA need to be ruled out. Presentation: 6/2/2024

9189 Medullary Thyroid Cancer Due To A Novel Ret Oncogene Mutation In A Patient On Glp-1 Receptor Agonist

Abstract Disclosure: K. Lamar: None. D. John: None. O. Faour: None. N. Meda: None. M. Kinaan: None. Introduction: Mutations in the RET oncogene have been associated with increased risk of endocrine neoplasia and Medullary Thyroid Cancer (MTC). We report the case of a patient who has a (c.3281G&amp;gt;A) RET mutation, previously reported as a variant of uncertain significance. Case: A 51-year-old lady presented to our endocrine clinic for routine management of hypothyroidism, type 2 diabetes mellitus, and obesity. She had been on liraglutide, metformin, glipizide, and basal insulin for several years with good diabetes management. She had also been on levothyroxine for more than 10 years. On physical examination, a right thyroid lobe nodule was palpated. We performed a neck ultrasound which revealed a solid, isoechoic nodule measuring (1.23 x 1.42 x 2.00 cm) with no calcifications. Fine needle aspiration was consistent with MTC. She denied family history of thyroid cancer. She was advised to stop liraglutide immediately given risk of MTC with GLP-1 receptor agonist use. Preoperative calcitonin and CEA were markedly high at 935 pg/mL and 60.3 ng/mL, respectively. Fortunately, Gallium Ga-68 dotatate PET CT showed no signs of metastatic disease. The patient underwent a total thyroidectomy with bilateral central and lateral neck dissection. No cervical metastases were noted on lymph node dissection. Genetic tumor testing demonstrated a mutation in the RET oncogene (c.3281G&amp;gt;A), which was previously reported as a variant with unknown significance. Screening for hyperparathyroidism and pheochromocytoma was normal. Postoperative calcitonin and CEA were &amp;lt;2.0 pg/mL and 3.2 ng/mL respectively. The patient continues MTC surveillance under the care of a multidisciplinary team. Discussion: Our case is the first case in literature that identifies the RET oncogene (c.3281G&amp;gt;A) mutation as a pathogenic variant associated with MTC. It also emphasizes the need for close monitoring for thyroid nodules in patients on GLP-1 receptor agonists and pre-existing thyroid disease, through a comprehensive physical examination and neck ultrasound if needed. Presentation: 6/2/2024

8061 Factors Affecting Survival of Metastatic Medullary Thyroid Cancer: A Population-Based Study From Surveillance, Epidemiology, and End Results (SEER) Program

Abstract Disclosure: A. Abdelhameed: None. H. Ibrahim: None. M. Mortagy: None. Introduction: Medullary thyroid cancer (MTC) arises from parafollicular cells of the thyroid. 43% of patients with MTC have metastasis. It was shown that the overall 5-year survival of patients with MTC is 40.4%. The clinical course of MTC is highly variable. The Aim is to identify factors affecting survival of the metastatic MTC sub-population. Understanding these factors is important in treating these patients. Methods 340 patients: with metastatic MTC who were diagnosed from 1975 to 2020 were extracted from SEER after removing duplicates and those not diagnosed by positive histology or cytology. Survival analysis was conducted, and Kaplan-Meier graph was generated. Univariate Cox regression was performed for all variables and respective hazard ratios (HR) were produced. Multivariable cox regression was performed for statistically significant variables. Results: The cohort were 59% males with a median age of 60 years. Median survival for the cohort was 20 months with survival of 63%, 41% and 31% at 1, 3, and 5 years respectively. Univariate Cox regression was statistically significant for age (HR 1.02), brain metastasis (HR 2.70), liver metastasis (1.65), lung metastasis (1.42), not performing total thyroidectomy (HR 2.77), lymph node ratio (HR 2.45), and systemic therapy after surgery (HR 0.34). Univariate Cox regression was not statistically significant for sex, grade, radiotherapy, chemotherapy, treatment delay, bone metastasis, distant lymph node metastasis, multifocal cancer, total number of benign and malignant tumors, race/ethnicity, income, tumor size and living in rural areas. Multivariable cox regression was done after inclusion of all significant variables from univariate Cox regression. It was only significant for age (HR 1.04), presence of lung metastasis (HR 1.91), and systemic therapy before surgery (HR 14.41). Conclusion: Increasing age, presence of lung metastasis and systemic therapy before surgery lead to worse prognosis in metastatic MTC. Gender, grade, radiotherapy, chemotherapy, treatment delay, bone or brain or liver metastasis, presence of multifocal cancer, race, tumor size and surgery don't affect survival according to multivariable cox regression. Future research is needed to study this group of patients. Presentation: 6/2/2024