Poorly Differentiated Thyroid Cancer Research Articles

Neoadjuvant Treatment of Locally Advanced Thyroid Cancer: A Preliminary Latin American Experience.

Surgical resection is not always achievable in thyroid cancer patients. Neoadjuvant therapy is rarely used, but recent trends favor multikinase inhibitors or selective tyrosine kinase inhibitors. These aim to reduce tumor volume, enabling previously unfeasible surgeries. Consecutive patients with locally advanced malignant thyroid tumors who received systemic therapies with a neoadjuvant intention were included in this retrospective multicenter case series conducted in five Latin American referral centers. Primary outcomes were pre- versus post-neoadjuvant response evaluations using the Response Evaluation Criteria in Solid Tumors, feasibility of surgery and completeness of resection. Secundary outcomes were mortality and status at last visit. Twenty-seven patients were included in this analysis. Patients with unresectable differentiated thyroid cancer (DTC) or poorly differentiated thyroid cancer (PDTC) received sorafenib (n=6) or lenvatinib (n=12), those with medullary thyroid cancer (MTC) were treated with vandetanib (n=5) or selpercatinib (n=1), and those with anaplastic thyroid cancer (ATC) harboring a BRAF V600E mutation (n=3) received dabrafenib and trametinib. The median patient age was 66 years (range 12-82), and 52% of the patients were female. In patients with PTC and PDTC, the median reduction in the diameter of the primary tumor was 25% (range 0-100%) after a median of 6 months of treatment. Surgical intervention was performed in ten (55%) of the patients. Among these, six patients (60%) achieved R0/R1 resection status. Six patients with MTC had a median reduction in tumor diameter of 24.5% (range 1-49) after a median treatment time of 9.5 months. Only one patient receiving selpercatinib, with a tumoral reduction of 25%, could undergo surgery, resulting in an R2 resection due to extensive mediastinal extension.Three patients with ATC showed a median tumor diameter reduction of 42% (range 6.7-50) after a median treatment time of 2 months. Two patients underwent surgical intervention and achieved R1 and R2 resection, respectively. While neoadjuvant therapy achieved tumoral responses, surgical resection was feasible in 50% of DTC, 33% of ATC, and 16% of MTC patients, with R0/R1 resection in 26% of the cohort, underscoring the need for patient selection and further research in this area.

Poorly differentiated thyroid cancer: Clinical, pathological, mutational, and outcome analysis.

Poorly differentiated thyroid cancer (PDTC) remains a challenge not only for pathologists and surgeons because of the difficulties associated with the diagnostic process and the compelling need for difficult thyroidectomy, but it is also of high clinical relevance because it is responsible for mortality in non-anaplastic follicular cell-derived thyroid cancer. Cases of PDTC within a 30-year period were reviewed by two independent pathologists. Histological features like atypical mitosis, necrosis, capsular, and vascular invasion were studied. Mutation analysis was done for BRAF, RET/PTC, RAS, and PI3KCA, and P53 was performed using immunohistochemistry. There were 39 patients with a median age of 53 years; 14 patients were more than 55 years of age. At presentation, 38.4% had compressive features and the median tumor size was 9 cm. At presentation, 67.7% had an extrathyroidal extension (ETE). R0 resection was achieved in 41%, with 12 cases resulting in a difficult thyroidectomy. Necrosis was seen in 65.7% and mitosis in 73.3% with well-differentiated components in 41%. The commonest mutation was RAS (23.1%). Survival was higher in the operable group (54.26, 95% confidence interval [CI]: 30.83-77.70 vs. 20.25, 95% CI: 0-54.07) months, respectively; however, 10-year survival was only 5% and only the tumor size and presence of mitosis were independent risk factors. PDTC presents with worrisome features like large size, ETE, and rapid growth. Aggressive surgical resection with extended/radical thyroidectomy may result in better loco-regional control and improved survival. RAS was the frequent mutation detected. It is worthwhile to identify prognostic factors that can predict the course of PDTC.

Comparative study between poorly differentiated thyroid cancer and anaplastic thyroid cancer: real-world pathological distribution, death attribution, and prognostic factor estimation.

The clinic-pathological boundary between poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) is unclear due to a wide spectrum of histopathological features and the rarity of the disease. In addition to that, with the highest mortality rate and non-standard treatment modality, the PDTC/ATC population has not been subjected to comprehensive description and comparison with the extent of histological characteristics, therapeutic response, prognostic factors, and death attribution analysis. A total of 4,947 PDTC/ATC patients from 2000 to 2018 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. Kaplan-Meier survival curve estimation and Cox proportional hazard regression were applied. Overall, the 5- and 10-year DSS for PDTC were 71.9% and 68.0%, respectively, whereas the 5- and 10-year OS are 59.3% and 51.2%, respectively. The median survival time for ATC patients was 3 months with 1-year OS being 26.9% and 1-year DSS being 31.2%. During the follow-up period, 68.1% of the PDTC/ATC cohort were dead, 51.6% of which were attributed to thyroid malignancies and 16.5% to non-thyroid causes. The top three common non-thyroid causes of death were miscellaneous cancers, lower respiratory system disease, and heart disease. The histological feature of papillary thyroid cancer (PTC) was the leading pathological category for PDTC patients (51.7%), whereas 76.7% of ATC patients' pathological feature was characterized as unidentifiable. Sarcoma histological characteristics found in ATC cases suffer the highest overall mortality (vs. PTC, HR = 2.61, 95% CI 1.68-4.06, P < 0.001). Older age unidentifiable histology feature, more advanced AJCC N1b, AJCC M1, and SEER stage, tumor size larger than 5cm, and more invasive tumor extension were independent bad outcome predictors. The populational analysis of the PDTC/ATC cohort has provided reliable support for better understanding of the difference between PDTC and ATC cases and the guidance of clinical practice and further studies.

Selenomethionine Suppress the Progression of Poorly Differentiated Thyroid Cancer via LncRNA NONMMUT014201/miR-6963-5p/Srprb Pathway.

Poorly differentiated thyroid cancer (PDTC) is a special type of thyroid cancer that threatens the life of the patients. Unfortunately, there are no effective treatments for PDTC right now, so it is urgent to search for new efficacious drugs. This experiment was designed to elucidate the effects of selenomethionine (SeMet) on PDTC in vitro and vivo. A xenograft animal model was used to assay the volume and weight of PDTC. LncRNA NOMMMUT014201 expression was detected by fluorescence in situ hybridization and Real-time quantitative PCR (qRT-PCR). In vitro experiments were carried on in WRO cells. The Cell Counting Kit-8 assay was performed to test the effect of SeMet on the proliferation of cells. And the migration and invasion of WRO cells by the wound-healing assay, Transwell migration and invasion assays. The cell apoptosis was measured by flow cytometry. In addition, genes related to proliferation, migration, invasion and apoptosis were detected through qRT-PCR and Western Blot. SeMet inhibited the proliferation, migration and invasion and promoted the apoptosis of WRO cells in a dose-dependent manner. Then vivo, SeMet significantly suppressed the volume and weight of PDTC. And SeMet downregulated the expressions of Ki67, PCNA, MMP2, MMP9 and BCL2, but upregulated that of BAX and Cleaved-Caspase 3. Moreover, SeMet upregulated the level of LncRNA NOMMMUT014201 both vivo and in vitro. In addition, repression of LncRNA NOMMMUT014201 removed the inhibition effect of SeMet on WRO cell growth significantly (p<0.05). Further investigation showed that LncRNA NOMMMUT014201 downregulated the expression of miR-6963-5p in PDTC cells, but miR-6963-5p inhibited the level of Srprb. In addition, sh-LncRNA NOMMMUT014201 enhanced the proliferation, migration and invasion but inhibited the apoptosis of WRO cells. However, inhibited miR-6963-5p or overexpressed Srprb relieved the effects of sh-LncRNA NOMMMUT014201on WRO cells. Collectively, SeMet inhibits the growth of PDTC in a dose-dependent manner through LncRNA NONMMUT014201/miR-6963-5p/Srprb signal pathway, thus suggesting that SeMet might be a potential drug for PDTC treatment.

Characterization of the Thyroid Cancer Genomic Landscape by Plasma-Based Circulating Tumor DNA Next-Generation Sequencing.

Background: The limited availability of targeted therapies in thyroid cancer (TC) has challenged conventional treatment algorithms and has established urgency for the identification of targetable genomic abnormalities. In addition to widely adopted tissue-based next-generation sequencing (NGS), plasma-based circulating tumor DNA (ctDNA) NGS is rapidly emerging as a genomic biomarker detection method and is steadily gaining utility across solid tumors. To date, plasma-based genomic alterations in TC have not been determined. Herein, we profile potential actionable mutations detected through ctDNA in patients with TC subtypes. Methods: A retrospective data analysis of the Guardant Health, Inc. database was performed using the commercially available Guardant360® plasma-NGS test on TC samples from adult patients collected between 2016 and 2021. The landscape of genomic alterations and blood tumor mutation burden (bTMB) were analyzed in patients with different types of TC: anaplastic TC (ATC), papillary TC (PTC), follicular TC (FTC), oncolytic carcinoma of the thyroid (OCA), poorly differentiated TC (PDTC), medullary TC (MTC), and TC not otherwise specified (TC NOS). Results: Of the 1094 patients included most of the patients n = 876 had TC NOS, and 20% had a specific diagnosis (92 ATC, 62 PTC, 14 FTC, 16 OCA, 2 PDTC, and 32 MTC patients). The median age was 65 (range 10-98) and 47.3% were male. 78.3% of patients had one or more genomic alteration detected by ctDNA NGS. TP53 (46.9%) was the most common mutation detected among all TC. BRAFV600E was detected in 27.2% of ATC, 35.7% of PTC, and in none of FTC. RAS was detected in 18.5% of ATC, 11.9% of PTC, and 62.5% of FTC. RET, ALK, and NTRK fusions were seen in 1.1%, 0.5%, and 0.2% of all TC, respectively. RET mutations were detected in 66.7% of MTC. bTMB analysis was performed on 159 patients. The mean bTMB was higher in ATC compared with other types of TC (p = 0.0011, 0.0557, and <0.0001, respectively). Conclusions: Plasma-based comprehensive NGS is a promising NGS method in TC; however, future validation of the clinical utility by analysis of paired tumor and plasma samples is needed.

Brusatol attenuated proliferation and invasion induced by KRAS in differentiated thyroid cancer through inhibiting Nrf2.

Poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) can be developed from differentiated thyroid cancer, and this dedifferentiated transformation leads to poor prognosis and high mortality. The role of Nrf2 in the dedifferentiation of differentiated thyroid cancer (DTC) induced by KRAS remains unclear. In this study, two DTC cell lines, BCPAP and WRO, were used to evaluate the function of Nrf2 in the dedifferentiation caused by wild-type KRAS (KRAS-WT) and G12V point mutation KRAS (KRAS-G12V). The overexpression of KRAS-WT and KRAS-G12V increased the proliferative and invasive ability of BCPAP and WRO cells. Aggressive morphology was observed in KRAS-WT and KRAS-G12V overexpressed WRO cells. These results suggested that overexpression of KRAS-WT or KRAS-G12V may induce dedifferentiation in DTC cells. The expression of Nrf2 was increased by KRAS-WT and KRAS-G12V in DTC cells. In addition, compared with normal thyroid tissues, the expression of Nrf2 protein was considerably higher in thyroid cancer tissues on immunohistochemistry (IHC) staining, and the increased expression of Nrf2 indicated a poor prognosis of thyroid cancer. These results indicated that Nrf2 is the KRAS downstream molecule in thyroid cancer. Functional studies showed that the Nrf2 inhibitor Brusatol counteracted the proliferative and invasive abilities induced by KRAS-WT and KRAS-G12V in BCPAP and WRO cells. In addition, the xenograft assay further confirmed that Brusatol inhibits tumor growth induced by KRAS-WT and KRAS-G12V. Collectively, this study suggests that Nrf2 could be a promising therapeutic target in KRAS-mediated dedifferentiation of thyroid cancer.

SAT534 A Rare Case of Poorly Differentiated Thyroid Cancer With Extraordinary Limitations to Treatment

Abstract Disclosure: N. Shahid: None. L. Rudman: None. H. Maldonado Rivera: None. J. Chambi-Torres: None. J.A. Gonzalez: None. S. Valepu: None. A. Barco: None. N.H. Shaaban: None. E. Angueira: None. Background: Poorly differentiated thyroid cancer (PDTC) is a rare and aggressive form of follicular epithelial cell derived thyroid carcinoma, representing 3-5% of all thyroid cancers. As a subtype, PDTC is in a category that is between well differentiated thyrocyte malignancies and undifferentiated (anaplastic) thyroid carcinomas. Current guidelines for treatment of PDTC are not well defined. Case presentation: A 56-year-old male with a history of PDTC was admitted to the hospital directly from a correctional facility due to concern for metastasis. Patient had a total thyroidectomy performed just two months ago that revealed PDTC on surgical pathology. Recommendations at that time were to complete a full body PET-CT and follow up with radiation oncology for radiation and chemotherapy. Patient was also discharged on Synthroid 175 mcg daily for TSH suppression. However, the patient did not have any follow up appointments scheduled while at the facility. PET-CT showed stable FDG avid 2.4 cm lower right neck mass and 2 cm focus of mildly increased activity in the right lobe of the liver. On admission, a triple phase MRI liver protocol was ordered and showed a 15 mm hepatic lesion that was arterially enhancing with persistent enhancement in venous and delayed phase without dropping signal on T2 fat and additional hyperintensity on T2. Bilateral 1.7 cm adrenal nodule was also identified with relative hypointensity on T2. FNA of right neck mass was performed but did not yield sufficient tissue for pathology. Subsequent right neck exploration and skin biopsies were obtained and revealed benign fibroadipose tissue with focal fat necrosis in the thyroid and lobular capillary hemangioma in right back, left chest, and right abdomen. Patient’s status as an inmate continued to delay radiation and chemotherapy for PDTC with possible metastasis. The decision was made with the hematology/oncology inpatient consult team to perform RAI treatment with 138 mCI of I-131. Synthroid was held in anticipation of the RAI and whole body scan was ordered for 1 week after administration of I-131. Post ablation whole body scan showed intense radiotracer uptake over the region of the left and right thyroid glands and normal uptake in the stomach, small bowel, and urinary bladder. No other areas of radiotracer uptake were found. Conclusion: Diagnosis and treatment of PDTC is challenging and the social constraints as an inmate make it even more difficult to initiate appropriate therapy with radiation oncology follow up. Our case illustrates the implications of RAI ablation after total thyroidectomy in staging and therapy of PDTC. Given the intermediate histologic characteristics of PDTC, further investigation is required in the setting of metastasis and exploration of the benefits of early aggressive therapy, such as external beam radiotherapy. Presentation Date: Saturday, June 17, 2023

THU484 Distinct Genetic Characteristics In Follicular Thyroid Cancer With Different Metastatic Potentials

Abstract Disclosure: S. Kwak: None. E. Lee: None. Y. Park: None. Although most follicular thyroid cancers (FTCs) show excellent prognosis, more than 5% accompany distant metastasis, often diagnosed unexpectedly in the advanced stage. Genetic or genomic markers have been shown to be useful as a prognostic tool in many cancers, but it is unclear whether genetic markers predicting the metastatic potential of FTCs exist. To investigate, 11 pairs of matched formalin fixed paraffin embedded tissue samples of primary (PTM1) and metastatic tumors (MT) from FTC patients with distant metastasis were analyzed by whole exome sequencing. For validation, 78 unmatched FTC samples including 49 well-differentiated tumors, 15 poorly-differentiated tumors and 14 anaplastic thyroid cancer (ATC) samples were analyzed by targeted sequencing. Among the 11 paired PTM1 and MT tumors, 10 showed concordant driver mutations (NRAS, HRAS, DICER1, EIF1AX), and the TERT promoter mutation was concordantly found in 6 pairs. However, the concordance rate of other somatic mutations in paired samples were found to be only 16.2%. Other mutational characteristics such as mutational signatures and CNVs also differed, suggesting the independent subclonal evolution of the paired MT from the PTM1 after metastasis. Interestingly, the frequency of mutations including driver, TERT promoter, and other mutations was lower in primary tumors without metastases (PTM0). Mutational characteristics of PTM0 also differed from those of PTM1 and MT, suggesting that the mutational or molecular characteristics of PTs at the time of diagnosis may distinguish metastatic potential. In a pooled analysis including published data of follicular patterned tumors, we found that metastatic or aggressive tumors were more likely to have the RAS mutation, which tended to be coupled with TERT, DICER1, EIF1AX, and TP53, gradually from minimally invasive FTC, widely invasive FTC to poorly differentiated thyroid cancer (PDTC) and ATC. Transcriptomic profiles from The Cancer Genome Atlas (TCGA) and our data (SNUH) showed RAS(+)/TERT(+) mutated tumors and RAS(+)/TERT(-) tumors had differences in several intracellular signal pathways. Therefore, when follicular neoplasm is diagnosed, NRAS and HRAS mutation tests followed by TERT promoter mutation tests may help diagnose FTCs with metastatic potential. Other genetic mutations could be candidates for a diagnostic or prognostic marker, and large-scale validation studies are warranted.This study was funded by the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Science, ICT &amp; Future Planning (NRF-2019R1A2C2084332). Presentation: Thursday, June 15, 2023

The Frequency of Differentiated Thyroid Cancer Recurrence in 2302 Patients With Excellent Response to Primary Therapy.

Discrepant data on the recurrence rate of differentiated thyroid cancer (DTC) are reported. To evaluate the frequency and risk factors of true recurrence in DTC patients with excellent responses (ExR) to initial therapy. A retrospective analysis of the 2302 consecutive DTC patients with ExR to primary therapy, treated during 24 years at single center. The percentage of recurrence and cumulative recurrence rate (CRR) were analyzed. Risk factors for recurrence for patients with papillary thyroid cancer (PTC) were investigated and methods for establishing a diagnosis of recurrence were evaluated. Of DTC patients, 32 (1.4%) experienced recurrence. PTC patients with recurrence were more likely to have younger age (P = .0182), larger tumor size (P = .0013), lymph node metastases (P = .0013), incomplete resection (P = .0446), higher ATA risk (P = .0002), and had more frequently been treated with 131I (P = .0203). CRRs at 5, 10, 15, 20, and 24 years after surgery were 1.2%, 1.9%, 2.5%, 2.9%, and 2.9%, respectively. The CRRs according to histological type were highest for poorly differentiated thyroid cancer (PDTC), lower for oncocytic (OTC) and follicular thyroid cancer (FTC), and lowest for PTC. Most recurrences occurred within the first 5 years of observation. The most effective method for detecting local recurrence was ultrasonography with fine needle aspiration cytology, and for distant metastases, 18F-FDG PET. True recurrence is rare in DTC patients. PTC patients with ExR to primary therapy and N0/Nx can be dismissed from oncological follow-up. Despite ExR to primary therapy, DTC patients with N1, and PDTC, OTC, FTC should remain under oncological follow-up.

Neutrophil-to-Lymphocyte Ratio Is Associated With the Proportion of Poorly Differentiated Components in Papillary Thyroid Carcinoma

IntroductionDiagnosis of poorly differentiated thyroid cancer (PDTC) requires ≥ 50% of poorly differentiated components (PDC) in Japan. However, the optimal cutoff percentage of PDC for PDTC diagnosis remains controversial. Although high neutrophil-to-lymphocyte ratio (NLR) correlates with the aggressiveness of papillary thyroid cancer (PTC), whether NLR is associated with the proportion of PDC in PTC remains unstudied. Materials and methodsPatients with the pure PTC (n = 664), PTC with < 50% PDC (n = 19), or PTC with ≥ 50% PDC (n = 26) who underwent surgery were retrospectively analyzed. Twelve-year disease-specific survival and preoperative NLR were compared among these groups. ResultsTwenty seven patients died from thyroid cancer. The PTC with ≥ 50% PDC group (80.7%) showed significantly worse 12-year disease-specific survival than the pure PTC group (97.2%) (P < 0.001); however, the < 50% PDC group (94.7%) did not (P = 0.91). The PTC with ≥ 50% PDC group had a significantly higher NLR than the pure PTC (P < 0.001) and the PTC with < 50% PDC groups (P < 0.001), whereas there was no significant difference in the NLR between the pure PTC and the PTC with < 50% PDC groups (P = 0.48). ConclusionsPTC with ≥ 50% PDC is more aggressive than either pure PTC or PTC with < 50% PDC, and NLR potentially reflects the PDC proportion. These results support the validity of 50% PDC as a cut-off for PDTC diagnosis and indicate the utility of NLR as a biomarker for PDC proportion.

Effect of postoperative radiotherapy for patients with differentiated thyroid cancer.

We evaluated the efficacy and safety of postoperative radiotherapy (PORT) for differentiated thyroid cancer (DTC) with high risk features. This retrospective study analyzed 187 patients treated for DTC from 1985 to 2019. DTC referred to nonanaplastic thyroid cancer originating from follicular cells. PORT was defined as the administration of external beam radiation to the thyroid and regional lymph nodes following surgery for initially diagnosed DTC. The patients were included in the analysis if they received PORT or exhibited any of the following features: (a) pT4 or pN1b according to the 8th American Joint Committee on Cancer, (b) poorly differentiated thyroid cancer (PDTC), or (c) unfavourable variants such as anaplastic foci and etc. After 1:1 propensity matching, a total of 108 patients were analyzed according to PORT receipt. The median follow-up duration of the matched group was 10.4 years. After matching, most of the variables became balanced, but the PORT group still had more PDTC and DTC with anaplastic foci. Radioactive iodine (RAI) was less frequently administered in the PORT group. PORT yielded a significantly higher 5-year locoregional recurrence free survival (LRFS) than the No PORT group (5-year LRFS 86.1% vs. 72.7%, p = 0.022), but the 10-year cancer specific survival (CSS) was similar between them (97.8% vs. 85.9%, p = 0.122). The multivariable analysis indicated that PORT was a favourable prognostic factor (Hazard ratio 0.3, 95% Confidence interval 0.1-0.8, p = 0.02) for LRFS, but not for CSS. Among 133 patients without PORT for initial disease, 39 of them received salvage surgery followed by salvage PORT. No severe toxicity after PORT was reported. PORT reduced locoregional recurrence in DTC patients without severe toxicity. PORT can be an effective and safe treatment to improve locoregional control in DTC with high risk features. However, further study is warranted to identify those who can benefit from PORT.

Molecular features of aggressive thyroid cancer.

Poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) have a worse prognosis with respect to well differentiated TC, and the loss of the capability of up-taking 131I is one of the main features characterizing aggressive TC. The knowledge of the genomic landscape of TC can help clinicians to discover the responsible alterations underlying more advance diseases and to address more tailored therapy. In fact, to date, the antiangiogenic multi-targeted kinase inhibitor (aaMKIs) sorafenib, lenvatinib, and cabozantinib, have been approved for the therapy of aggressive radioiodine (RAI)-resistant papillary TC (PTC) or follicular TC (FTC). Several other compounds, including immunotherapies, have been introduced and, in part, approved for the treatment of TC harboring specific mutations. For example, selpercatinib and pralsetinib inhibit mutant RET in medullary thyroid cancer but they can also block the RET fusion proteins-mediated signaling found in PTC. Entrectinib and larotrectinib, can be used in patients with progressive RAI-resistant TC harboring TRK fusion proteins. In addition FDA authorized the association of dabrafenib (BRAFV600E inhibitor) and trametinib (MEK inhibitor) for the treatment of BRAFV600E-mutated ATC. These drugs not only can limit the cancer spread, but in some circumstance they are able to induce the re-differentiation of aggressive tumors, which can be again submitted to new attempts of RAI therapy. In this review we explore the current knowledge on the genetic landscape of TC and its implication on the development of new precise therapeutic strategies.

Newly proposed survival staging system for poorly differentiated thyroid cancer: a SEER-based study.

Despite the recent release of the 8th edition TNM staging system, the risk stratification for poorly differentiated thyroid cancer (PDTC) remains controversial. Retrospective study. SEER database and the First Hospital of China Medical University (FHCMU) database. Between 2004 and 2015, 1201 PDTC patients from the SEER database were enrolled to propose a new staging system. 38 PDTC patients were included from the FHCMU. A retrospective analysis of 1201 PDTC cases was performed, and a new staging classification was developed as follows: stage I: age < 55 and T1/any N/M0 (n = 127, 10.57%); stage II: age < 55 and T2-4/any N/M0 or age ≥ 55 and T1-2/any N/M0 (n = 523, 43.55%); stage III: age < 55 and any T/N0/M1 or age ≥ 55 and any T3/any N/M0 (n = 239, 19.90%); stage IV: age < 55 and any T/N1/M1 or age ≥ 55 and T4/any N/M0, and T/any N/M1 (n = 312, 25.98%). The 10-year disease-specific survival rates of patients in the new stages I, II, III, and IV were 97.9%, 77.9%, 35.3%, and 12.1%, respectively. The proportion of variation explained (PVE) for disease-specific survival of the proposed system was higher than that of the 8th AJCC TNM staging (30.61% vs. 27.15%). The accuracy of the staging system was verified in 38 PDTC patients from the FHCMU. The proposed staging system provided a more accurate risk stratification for PDTC patients. The new staging model may facilitate the design of personalized treatment strategies for PDTC patients.

MMP1 acts as a potential regulator of tumor progression and dedifferentiation in papillary thyroid cancer.

Papillary thyroid cancer (PTC) is one of the malignancies with an excellent prognosis. However, in PTC, progression or dedifferentiation into poorly differentiated thyroid cancer (PDTC) or anaplastic thyroid cancer (ATC) extremely jeopardizes patients' prognosis. MMP1 is a zinc-dependent endopeptidase, and its role in PTC progression and dedifferentiation is unclear. In this study, transcriptome data of PDTC/ATC and PTC from the Gene Expression Omnibus and The Cancer Genome Atlas databases were utilized to perform an integrated analysis of MMP1 as a potential regulator of tumor progression and dedifferentiation in PTC. Both bulk and single-cell RNA-sequencing data confirmed the high expression of MMP1 in ATC tissues and cells, and further study verified that MMP1 possessed good diagnostic and prognostic value in PTC and PDTC/ATC. Up-regulated MMP1 was found to be positively related to more aggressive clinical characteristics, worse survival, extracellular matrix-related pathways, oncogenic immune microenvironment, more mutations, higher stemness, and more dedifferentiation of PTC. Meanwhile, in vitro experiments verified the high level of MMP1 in PDTC/ATC cell lines, and MMP1 knockdown and its inhibitor triolein could both inhibit the cell viability of PTC and PDTC/ATC. In conclusion, our findings suggest that MMP1 is a potential regulator of tumor progression and dedifferentiation in PTC, and might become a novel therapeutic target for PTC, especially for more aggressive PDTC and ATC.

OR09-3 Integrins as Potential Molecular Targets in Thyroid Cancer Imaging and Therapy

Abstract Background Integrins are cell adhesion receptors consisting of 24 transmembrane heterodimers generated from a combination of 18α integrin and 8β integrin subunits. A subset of integrins consists of receptors recognizing Arg-Gly-Asp (RGD) peptide motifs. One of the RGD-recognizing receptors is integrin αvβ3 that has been recently shown to play a role in neovascularization and progression of several cancers. Radiolabeled RGD analogs have emerged as potential imaging and therapeutic options in cancers characterized by a high expression of integrin αvβ3. Therefore, the aim of this study was to establish the expression of integrin αvβ3 in thyroid cancer (TC). Methods We analyzed the mRNA expression of integrin αvβ3 in 496 BRAF-like and RAS-like human TC tissue samples, including 65 paired samples of tumor vs normal tissue based on The Cancer Genome Atlas. We assessed the protein expression of integrin αvβ3 in 70 TC tissue samples and 10 normal thyroid tissues, as well as in 14 TC cell lines. BRAF-like or RAS-like tumor status was determined by BRS score based upon standard expression profiles ranging from -1 to 0 for BRAF-like cancer and 0 to 1 for RAS-like tumors. The association between BRS and αvβ3 expression was tested using the Spearman correlation coefficient (r). T-tests and paired T-tests were used to compare the continuous variables between the two groups as appropriate, and Kruskal-Wallis test was used for multiple group comparisons with an adjusted p-value of ≤ 0.05 as statistically significant. Results αv integrin subunit mRNA expression was significantly higher in TC than normal thyroid (log fold change 0.3, p=0.001), while the expression of the β3 subunit was similar between paired normal and malignant samples (log fold change -0.2, p=0.30). BRAF-like tumors were characterized by a higher mRNA expression of αvβ3 integrins as documented by a moderate negative correlation between BRS and αv (r=-0.5, p&amp;lt;0.001) as well as β3 (r=-0.27, p&amp;lt;0.001). Consistently, the BRAF-like TC cell lines OCUT2 (BRS=-1), TPC1 (BRS=-0.4), K1 (BRS=-0.29), as well as Hurthle cell TC cell line XTC1 (BRS=-0.46), were characterized by the highest αvβ3 mRNA and/or protein expression. Immunostaining revealed αv expression in all malignant samples, with classic papillary TC characterized by the highest expression as compared with follicular TC (p&amp;lt;0.001), poorly-differentiated TC (p=0.006) and normal thyroid (p&amp;lt;0.001). β3 protein expression had lower intensity than αv integrin and was present in 31.8% of papillary TC, 15% of follicular TC and was not detected in poorly-differentiated TC nor normal thyroid. Conclusions TC is characterized by a differential expression of αvβ3 integrin, which is particularly high in the most common type of TC - BRAF-like papillary TC. The αvβ3 integrin could potentially serve as a molecular target for imaging and therapy with radiolabeled RGD analogs in TC. Presentation: Saturday, June 11, 2022 12:00 p.m. - 12:15 p.m.

Target Therapy in Thyroid Cancer: Current Challenge in Clinical Use of Tyrosine Kinase Inhibitors and Management of Side Effects.

Thyroid cancer (TC) is the most common endocrine malignancy. TC is classified as differentiated TC (DTC), which includes papillary and follicular subtypes and Hürthle cell variants, medullary TC (MTC), anaplastic TC (ATC), and poorly differentiated TC (PDTC). The standard of care in DTC consists of surgery together with radioactive iodine (131I) therapy and thyroid hormone, but patients with MTC do not benefit from 131I therapy. Patients with advanced TC resistant to 131I treatment (RAI-R) have no chance of cure, as well as patients affected by ATC and progressive MTC, in which conventional therapy plays only a palliative role, representing, until a few years ago, an urgent unmet need. In the last decade, a better understanding of molecular pathways involved in the tumorigenesis of specific histopathological subtypes of TC has led to develop tyrosine kinase inhibitors (TKIs). TKIs represent a valid treatment in progressive advanced disease and were tested in all subtypes of TC, highlighting the need to improve progression-free survival. However, treatments using these novel therapeutics are often accompanied by side effects that required optimal management to minimize their toxicities and thereby enable patients who show benefit to continue treatment and obtain maximal clinical efficacy. The goal of this overview is to provide an update on the current use of the main drugs recently studied for advanced TC and the management of the adverse events.

Daily Management of Patients on Multikinase Inhibitors' Treatment.

In a minority of differentiated thyroid cancer (TC) cases and in a large percentage of poorly differentiated TCs (PDTCs) and anaplastic TCs (ATCs), the prognosis is poor due to the lack of response to conventional treatments. In the last two decades, multikinase inhibitor (MKI) compounds have been developed and demonstrated to be very effective in these aggressive cases. Besides the great efficacy, several adverse events (AEs) have been reported in virtually all patients treated with MKIs, largely overlapping between different compounds and including hypertension, diarrhea, anorexia, decreased weight, fatigue, and proteinuria. Most grade 3–4 adverse reactions occur during the first 6 months of treatment and require dosage reduction and/or drug discontinuation. Due to severity of the AEs related to the treatment with MKIs, a multidisciplinary team is definitely required for the daily management of these patients, for the evaluation of the disease status, and the psychophysical condition. Moreover, it is crucial that the patients could have a facilitated access to reach either specialist doctors or nurses who must have been trained to follow them for their individual clinical complications. The follow-up visits should take place at monthly intervals until the sixth month and then every 1–2 months until the completion of the first year of treatment. The flow chart followed at our tertiary center is reported in the present review as a real-life-based example for the follow-up of patients with advanced TC on MKI treatment.

Abstract 913: Tert mutant promoter mouse model induces cancer progression in BrafV600E-driven thyroid tumors: A novel tool to understand the biology of telomerase-reactivated cancers

Abstract Hotspot mutations in the proximal promoter of the telomerase reverse transcriptase (TERT) gene are the first cross-cancer alterations lying in a gene regulatory region. TERT promoter mutations (TPMs) are enriched in advanced thyroid tumors and constitute markers of disease severity. TPMs enhance TERT transcription, which is otherwise silenced in adult tissues, thus reactivating a bone fide oncoprotein. To study TERT deregulation and its downstream consequences in a biologically accurate model, we generated a Tert-mutant promoter mouse model via CRISPR/Cas9 editing of the equivalent murine locus and crossed these animals with thyroid-specific BrafV600E-mutant mice. BrafV600E animals develop highly penetrant papillary thyroid tumors (PTC) by week 5, but do not progress. In contrast, BrafV600E+TertMUT animals showed an increased incidence of poorly differentiated thyroid cancers (PDTC) by 20 weeks (30% vs. 0% in BrafV600E; chi-squared P= 0.03), mimicking those exhibited by an alternative transgenic model of Tert overexpression (BrafV600E+K5-Tert; 36% PDTCs). Mouse Tert promoter mutation increased Tert transcription in vitro and in vivo, as reported in patients’ tumors carrying TPMs. Braf+Tert animals partially responded to MAPK pathway inhibition (dabrafenib plus trametinib), showing that MAPK signaling remains relevant in these specimens. Interestingly, RNA sequencing of Tert-reactivated murine thyroid tumors showed unique transcriptomic profiles (compared to BrafV600E alone), suggesting that downstream effects, other than the canonical Tert-mediated telomere maintenance, operate in cancers harboring TPMs. These cancer models of telomerase reactivation provide excellent pre-clinical settings to understand the regulatory mechanisms and biological underpinnings of TPM-induced progression of thyroid and other tumors, and to explore novel therapeutic strategies. Citation Format: Inigo Landa, Jingzhu Hao, Bin Xu, Joseph Giacalone, Zach Herbert, Maria A. Blasco, Jeffrey A. Knauf, Ronald Ghossein, James A. Fagin. Tert mutant promoter mouse model induces cancer progression in BrafV600E-driven thyroid tumors: A novel tool to understand the biology of telomerase-reactivated cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 913.

Poorly Differentiated Thyroid Carcinoma: Single Institution Series of Outcomes.

Poorly differentiated thyroid cancer (PDTC) is a rare but aggressive subtype of thyroid cancer that portends a poor prognosis. There remains a paucity of literature on PDTC outcomes. The aim of our study was to evaluate outcomes of PDTC in our tertiary care facility. We identified all histologically confirmed PDTC cases from 1997-2018 treated at our Institution and collected data points in an IRB-approved registry. We then conducted a retrospective study to assess outcomes and identified factors associated with inferior outcomes. Twenty-three patients were identified with a median age at diagnosis of 60 years (range=39-89 years). Nineteen (83%) underwent total thyroidectomy. Eight (42%) patients had lymph node dissections and 2 (11%) underwent adjuvant radiation. Thirteen (68%) patients were treated with radioactive iodine (RAI). Those who underwent total thyroidectomy had a median overall survival (mOS) of 88 months, 5 year-OS of 56%, 5 year-local recurrence-free survival (LRFS) of 45%, and 5 year-distant recurrence-free survival (DRFS) of 36%. T4 disease had worse mOS (14 vs. 87 m, p=0.0082), and 5 year-LRFS rate (12 vs. 74%, p=0.0312) compared to T1-3. N0 disease had an improved mOS (172 vs. 32 m, p=0.0013), 5 year-LRFS rate (63 vs. 17%, p=0.0033), and 5 year-DRFS (57 vs. 0%, p=0.0252). Eight out of 23 patients (35%) were alive at last follow-up, with a median of 68 months (range=20-214). The most common cause of death was distant recurrence (73%). Six patients received systemic therapy with various tyrosine kinase inhibitors with a median duration on treatment of 7 months (range=1-30 months). Advanced T and N stage were factors associated with significantly inferior outcomes. While select patients benefited with systemic treatment, it remains unclear if intensified locoregional therapy should be considered in patients with PDTC.

Clinical Significance of Circulating Tumor Cells (CTCs) and Survivin on Predicting Prognosis in Thyroid Cancer Patients.

Background Clinical significance of circulating tumor cell (CTC) count, mesenchymal CTCs (MCTCs), and survivin in patients with thyroid cancer remains unclear. We evaluated the relationship between the expression of different CTC subtypes or survivin and the prognosis in patients with thyroid cancer. Patients and Methods. This study enrolled 164 patients with thyroid cancer who were diagnosed from January 2013 to September 2020 in our hospital. Among these patients, there were 73 cases with papillary thyroid cancer (PTC), 60 cases with follicular thyroid cancer (FTC), 12 medullary thyroid cancers (MTC), 10 poorly differentiated thyroid cancers (PDTC), 9 anaplastic thyroid cancers, and 10 control patients with nonmalignant thyroid nodules based on their histopathological characteristics. Only 5 milliliters (mL) of peripheral blood from the patients with thyroid cancer and control was used to detect the CTC cell number via CanPatrol capture technique before treatments. We also isolated mononuclear cells (MNC) from the peripheral blood and performed quantity reverse transcriptase polymerase chain reaction (qPCR) for survivin gene expression among these patients. Results The overall positive rates of CTC at diagnosis were 56.1%. The relapse and metastasis rates in PTC and FTC patients with more than 6 CTCs and positive MCTCs were significantly higher than those in the patients with 6 or less than 6 CTCs and MCTCs. It was also found that these patients with >6 CTCs and MCTCs had shorter progression-free survival (PFS). Additionally, the survivin level of the patients with thyroid cancer was strongly relative to differentiation grades of thyroid cancers. Conclusions The detection of more than six of total CTCs and positive MCTCs in the patients with differentiated thyroid cancer is an excellent biomarker for predicting the prognosis of patients. Survivin also is a good biomarker for thyroid cancer differentiation.