Fluorodeoxyglucose Positron Emission Research Articles

Integrating [18F]-Fluorodeoxyglucose Positron Emission Tomography with Computed Tomography with Radiation Therapy and Immunomodulation in Precision Therapy for Solid Tumors.

[18F]-FDG positron emission tomography with computed tomography (PET/CT) imaging is widely used to enhance the quality of care in patients diagnosed with cancer. Furthermore, it holds the potential to offer insight into the synergic effect of combining radiation therapy (RT) with immuno-oncological (IO) agents. This is achieved by evaluating treatment responses both at the RT and distant tumor sites, thereby encompassing the phenomenon known as the abscopal effect. In this context, PET/CT can play an important role in establishing timelines for RT/IO administration and monitoring responses, including novel patterns such as hyperprogression, oligoprogression, and pseudoprogression, as well as immune-related adverse events. In this commentary, we explore the incremental value of PET/CT to enhance the combination of RT with IO in precision therapy for solid tumors, by offering supplementary insights to recently released joint guidelines.

Pathologically confirmed spontaneous regression of small cell lung cancer after computed tomography-guided percutaneous transthoracic needle biopsy followed by surgery

BackgroundSpontaneous regression of malignant tumors is a rare phenomenon, especially in primary lung cancer. The underlying mechanisms remain unclear, but they may often involve immunological mechanisms.Case presentationIn January 2020, a 78-year-old female underwent examination during follow-up of interstitial pneumonia. Chest X-ray and computed tomography (CT) scan revealed a 1.2 × 1.2 cm nodule in the left lower lobe. Based on CT-guided percutaneous transthoracic needle biopsy (PTNB), it was diagnosed as small cell lung cancer (SCLC). Immunohistochemical staining showed that tumor cells were positive for CD56, synaptophysin, and chromogranin A. Twenty-three days after the CT-guided PTNB, repeat CT scan showed that the tumor size regressed to 0.6 × 0.6 cm. The tumor showed positive uptake in fluorodeoxyglucose (FDG) positron emission tomography (PET)–CT. The maximum standardized uptake value of the nodule was 2.24. PET–CT and enhanced magnetic resonance imaging of the brain showed no distant or lymph node metastasis. The patient’s preoperative disease was diagnosed as cT1aN0M0, stageIA1, SCLC. In March 2020, she underwent left lower lobectomy and mediastinal lymph node dissection. Pathological examination of the resected specimen showed that the small tumor cells were dense with a high nucleus to cytoplasm ratio, and the morphological diagnosis was small cell carcinoma. The resected tumor size regressed to 0.05 × 0.02 cm, and no lymph node metastasis was observed. Because it was extremely small, immunohistochemical staining could not be conducted. Active fibrosis and inflammation were present around the tumor. Finally, the patient was pathologically diagnosed as SCLC pT1miN0M0, stage IA1. The patient is alive without recurrence 23 months after surgery with no adjuvant therapy.ConclusionsWe present a rare surgical case of pathologically confirmed spontaneous regression of SCLC after CT-guided PTNB. Although spontaneous regression is extremely rare, we should recognize this phenomenon.

Arterial spin labeling (ASL-MRI) versus fluorodeoxyglucose-PET (FDG-PET) in diagnosing dementia: a systematic review and meta-analysis

BackgroundDementia is generally caused by neurodegenerative diseases affecting the brain, which leads to a progressive neurocognitive decline characterized by inability to perform major higher functioning tasks. Fluorodeoxyglucose-positron emission tomography (FDG-PET) scan is one of the main imaging tests performed for diagnostic purposes. However, with FDG-PET being quite expensive and not widely available, an attempt to find an alternative is set. Arterial-spin-labelling magnetic resonance imaging (ASL-MRI) is an increasingly investigated substitute to FDG-PET for the diagnosis of dementia. Thereby, the main purpose of this systematic review and meta-analysis is to compare the diagnostic ability of FDG-PET and ASL-MRI in detecting dementia.MethodsPRISMA checklist for diagnostic test accuracy was employed in outlining this paper. A literature search was done using several search engines including PubMed, Core, and Cochrane. Two researchers (HH and SH) extracted the essential information from all included articles. Risk of bias was evaluated by the Quality Assessment of Diagnostic Accuracy Studies tool, version 2 (QUADAS-2). A qualitative analysis and summary of studies’ results were provided. In addition, a meta-analysis was executed based on the studies which involved sensitivity and specificity measures of diagnostic accuracy.ResultsFourteen total studies were included in the given review. Qualitative analysis of the articles showed that nine studies demonstrated an overlap between metabolic and perfused brain maps as derived by FDG-PET and ASL-MRI respectively, while the remaining five studies registered significant differences across both modalities, with superiority to FDG-PET. As for the meta-analysis implemented, summary ROC-curve analysis revealed that FDG-PET performed better than ASL-MRI, with pooled sensitivity being significantly higher for FDG-PET.ConclusionsComparing the diagnostic value of FDG-PET and ASL-MRI, the results of this systematic review and meta-analysis indicate that FDG-PET still has an advantage over ASL-MRI. Such implication could be related to the technical differences relating to both modalities, with ASL-MRI having lower temporal resolution. It’s worth mentioning that specificity was rather quite similar among both modalities and some studies found an overridden metabolic and perfused images. These findings call for future research to focus their scope of investigation while exploring the diagnostic value of ASL-MRI.

Explainable Vision Transformer with Self-Supervised Learning to Predict Alzheimer's Disease Progression Using 18F-FDG PET.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects millions of people worldwide. Early and accurate prediction of AD progression is crucial for early intervention and personalized treatment planning. Although AD does not yet have a reliable therapy, several medications help slow down the disease's progression. However, more study is still needed to develop reliable methods for detecting AD and its phases. In the recent past, biomarkers associated with AD have been identified using neuroimaging methods. To uncover biomarkers, deep learning techniques have quickly emerged as a crucial methodology. A functional molecular imaging technique known as fluorodeoxyglucose positron emission tomography (18F-FDG-PET) has been shown to be effective in assisting researchers in understanding the morphological and neurological alterations to the brain associated with AD. Convolutional neural networks (CNNs) have also long dominated the field of AD progression and have been the subject of substantial research, while more recent approaches like vision transformers (ViT) have not yet been fully investigated. In this paper, we present a self-supervised learning (SSL) method to automatically acquire meaningful AD characteristics using the ViT architecture by pretraining the feature extractor using the self-distillation with no labels (DINO) and extreme learning machine (ELM) as classifier models. In this work, we examined a technique for predicting mild cognitive impairment (MCI) to AD utilizing an SSL model which learns powerful representations from unlabeled 18F-FDG PET images, thus reducing the need for large-labeled datasets. In comparison to several earlier approaches, our strategy showed state-of-the-art classification performance in terms of accuracy (92.31%), specificity (90.21%), and sensitivity (95.50%). Then, to make the suggested model easier to understand, we highlighted the brain regions that significantly influence the prediction of MCI development. Our methods offer a precise and efficient strategy for predicting the transition from MCI to AD. In conclusion, this research presents a novel Explainable SSL-ViT model that can accurately predict AD progress based on 18F-FDG PET scans. SSL, attention, and ELM mechanisms are integrated into the model to make it more predictive and interpretable. Future research will enable the development of viable treatments for neurodegenerative disorders by combining brain areas contributing to projection with observed anatomical traits.

A MALT LYMPHOMA PRESENTING WITH PRIMARY DIFFUSE RENAL INVOLVEMENT

The involvement of kidney in marginal zone lymphoma is not a frequent condition. Seventy-seven-year-old female presented with renal failure. Renal biopsy revealed diffuse lymphoid infiltration replacing the normal renal tissue. Immunohistochemical staining was CD20, CD38, kappa, IgD positive and CD3, lambda, cyclin D1, CD5, CD23, CD43 negative. Ki-67 was 10% positive. The patient was diagnosed as MALT type marginal zone lympho-ma. Body Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) performed for staging revealed diffuse FDG uptake in both kidneys and no lym-phadenopathy was detected. Bone marrow aspiration and biopsy were normal. Rituximab - bendamustin chemotherapy regimen was started. In conclusion, this is the first case of MALT lymphoma involving kidney diffusely which requires rapid diagnosis and treatment to prevent irreversible loss of renal functions.

18F]fluorodeoxyglucose positron emission tomography/computed tomography characteristics of primary mediastinal germ cell tumors

Primary mediastinal germ cell tumor (MGCT) is an uncommon tumor. Although it has histology similar to that of gonadal germ cell tumor (GCT), the prognosis for MGCT is generally worse than that for gonadal GCT. We performed visual assessment and quantitative analysis of [18F]fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) for MGCTs. A total of 35 MGCT patients (age = 33.1 ± 16.8 years, F:M = 16:19) who underwent preoperative PET/CT were retrospectively reviewed. The pathologic diagnosis of MGCTs identified 24 mature teratomas, 4 seminomas, 5 yolk sac tumors, and 2 mixed germ cell tumors. Visual assessment was performed by categorizing the uptake intensity, distribution, and contour of primary MGCTs. Quantitative parameters including the maximum standardized uptake value (SUVmax), tumor-to-background ratio (TBR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and maximum diameter were compared between benign and malignant MGCTs. On visual assessment, the uptake intensity was the only significant parameter for differentiating between benign and malignant MGCTs (p = 0.040). In quantitative analysis, the SUVmax (p < 0.001), TBR (p < 0.001), MTV (p = 0.033), and TLG (p < 0.001) showed significantly higher values for malignant MGCTs compared with benign MGCTs. In receiver operating characteristic (ROC) curve analysis of these quantitative parameters, the SUVmax had the highest area under the curve (AUC) (AUC = 0.947, p < 0.001). Furthermore, the SUVmax could differentiate between seminomas and nonseminomatous germ cell tumors (p = 0.042) and reflect serum alpha fetoprotein (AFP) levels (p = 0.012). The visual uptake intensity and SUVmax on [18F]FDG PET/CT showed discriminative ability for benign and malignant MGCTs. Moreover, the SUVmax may associate with AFP levels.

Deep learning based diagnosis of Alzheimer’s disease using FDG-PET images

PurposeThe aim of this study is to develop a deep neural network to diagnosis Alzheimer's disease and categorize the stages of the disease using FDG-PET scans. Fluorodeoxyglucose positron emission tomography (FDG-PET) is a highly effective diagnostic tool that accurately detects glucose metabolism in the brain of AD patients. Material and methodsIn this work, we have developed a deep neural network using FDG-PET to discriminate Alzheimer's disease subjects from stable mild cognitive impairment (sMCI), progressive mild cognitive impairment (pMCI), and cognitively normal (CN) cohorts. A total of 83 FDG-PET scans are collected from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, including 21 subjects with CN, 21 subjects with sMCI, 21 subjects with pMCI, and 20 subjects with AD. ResultsThe method has achieved remarkable accuracy rates of 99.31% for CN vs. AD, 99.88% for CN vs. MCI, 99.54% for AD vs. MCI, and 96.81% for pMCI vs. sMCI. Based on the experimental results. ConclusionThe results show that the proposed method has a significant generalisation ability as well as good performance in predicting the conversion of MCI to AD even in the absence of direct information. FDG-PET is a well-known biomarker for the identification of Alzheimer's disease using transfer learning.

Imaging prediction of KRAS mutation in patients with rectal cancer through deep metric learning using pretreatment [18F]Fluorodeoxyglucose positron emission tomography/computed tomography.

To predict KRAS mutation in rectal cancer (RC) through computer vision of [18F]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) by using metric learning (ML). This study included 160 patients with RC who had undergone preoperative PET/CT. KRAS mutation was identified through polymerase chain reaction analysis. This model combined ML with the deep-learning framework to analyze PET data with or without CT images. The Batch Balance Wrapper framework and K-fold cross-validation were employed during the learning process. A receiver operating characteristic (ROC) curve analysis was performed to assess the model's predictive performance. Genetic alterations in KRAS were identified in 82 (51%) tumors. Both PET and CT images were used, and the proposed model had an area under the ROC curve of 0.836 for its ability to predict a mutation status. The sensitivity, specificity, and accuracy were 75.3%, 79.3%, and 77.5%, respectively. When PET images alone were used, the area under the curve was 0.817, whereas the sensitivity, specificity, and accuracy were 73.2%, 79.6%, and 76.2%, respectively. The ML model presented herein revealed that baseline 18F-FDG PET/CT images could provide supplemental information to determine KRAS mutation in RC. Additional studies are required to maximize the predictive accuracy. The results of the ML model presented herein indicate that baseline 18F-FDG PET/CT images could provide supplemental information for determining KRAS mutation in RC.The predictive accuracy of the model was 77.5% when both image types were used and 76.2% when PET images alone were used. Additional studies are required to maximize the predictive accuracy.

Large mesenchymal cystic and chondroid pulmonary hamartoma mimicking lung cancer: Case report

Pulmonary hamartoma is the most commonly resected benign neoplasm of lung. The mesenchymal cystic subtype is a rare and often bilaterally occurring variant composed of multiple cysts and nodules. Herein, we present an asymptomatic 70-year-old woman with a large and mostly cystic growth of right hilar region. Computed tomography of the chest and fluorodeoxyglucose positron emission tomography/computed tomography imaging traced its origins to right middle lobe. Overall features suggested primary lung cancer or perhaps other cystic lung disease.Because transbronchial lung biopsy failed to establish a histologic diagnosis, right middle lobectomy was undertaken by video-assisted thoracoscopic surgery. The gross surgical specimen harbored a single and sizeable (8.0 × 4.0 cm) cystic lesion containing multiple yellow-white nodules. A diagnosis of mesenchymal cystic and chondroid hamartoma was ultimately rendered. This particular case is noteworthy, given the initial clinical resemblance to primary lung cancer.

A - 59 Regional Cerebral Metabolism Is Associated with Performance on the Visual Object and Space Perception Battery in those with Posterior Cortical Atrophy.

Posterior cortical atrophy (PCA) is a relatively rare clinical syndrome characterized by visuoperceptual/spatial dysfunction with relatively preserved memory, language, and insight in the early stages. Thus, PCA provides a unique population through which to evaluate structure-function relationships for commonly used neuropsychological tests. Here, we evaluated relationships between fluorodeoxyglucose (FDG) positron emission tomography (PET) and performance on the Visual Object and Space Perception (VOSP) Battery. Ten participants with an established diagnosis of PCA underwent baseline neuropsychological testing that included the VOSP, FDG-PET, and structural MRI. We used FreeSurfer to identify anatomical structures in the structural MRI scans, aligned the MRI and PET scans, and then extracted FDG signal from these same regions. Several brain regions relevant for PCA were a priori targeted. We evaluated relationships between the regional FDG values and VOSP performances using Spearman's rank correlation. Silhouettes, Dot Counting, and Number Location showed strong relationships with the superior parietal lobule bilaterally. The right superior parietal lobule showed moderate to strong relationships with Incomplete Letters and Progressive Silhouettes, whereas the left superior parietal lobule showed a strong relationship with Object Decision. Incomplete letters showed a strong relationship with the right supramarginal gyrus. Silhouettes showed a strong relationship with the left fusiform gyrus. These findings from a relatively rare and heterogeneous syndrome provide insight into the regional contributions to visuospatial functioning. Future work will evaluate network-level integrity with these tasks in order to further clarify structure-function relationships.

A - 40 Assessment of Dementia with Lewy Bodies in a Patient with both Characteristic and Atypical Features.

Dementia with Lewy Bodies (DLB) is the second most common neurodegenerative dementia after Alzheimer disease (ad). Its heterogeneous presentation and overlapping features with other dementias result in frequent misdiagnosis, which can delay optimal management. The present case illustrates complex symptomology, comprehensive assessment, and diagnostic challenges in a patient with DLB. A 64-year-old female presented to an academic medical center neurology clinic with rapid cognitive deterioration over the past 1.5years accompanied by visual disturbances, psychiatric and behavioral changes, and mild motor symptoms. Initial differential included Creutzfeldt-Jakob disease, atypical parkinsonism, frontotemporal lobar degeneration (FTLD), encephalopathy, and ad. Work-up in included neuropsychological, neuroimaging, cerebral spinal fluid (CSF), electroencephalogram (EEG), and skin biopsy assessments. Neuropsychological interview revealed fluctuating attention/alertness, visual hallucinations, hyposmia, paranoid and repetitive behaviors, and subtle evidence for dream enactment. Her cognitive profile showed global impairment with pronounced visuospatial and executive deficits. Recognition memory, verbal reasoning, and naming were relatively well-preserved. Magnetic resonance imaging showed mild atrophy; fluorodeoxyglucose positron emission tomography (PET) showed hypometabolism in frontal and temporal regions whereas uptake was highest in the occipital lobes and basal ganglia; skin biopsy was positive for synucleinopathy; CSF and EEG were broadly unrevealing. The preponderance of data was consistent with diagnostic criteria for probable DLB. Skin biopsy increased diagnostic confidence. Atypical features included relatively rapid cognitive decline, minimal parkinsonism, and PET imaging suggesting FTLD. The present case highlights the utility of a multidisciplinary approach (e.g., neurological exam, detailed symptom screening, neuropsychological testing, and advanced laboratory assessments) in a complex case of DLB.

A - 84 Neuropsychological Phenotypes of FDG-PET Identified Corticobasal Degeneration Pathology.

Corticobasal degeneration (CBD), a rare neurodegenerative disorder, can present with diverse clinical phenotypes. This qualitative case series examines clinical progression of neuropsychological findings associated with CBD identified pathology on fluorodeoxyglucose-positron emission tomography (FDG-PET). Three clinically referred older adults underwent neuropsychological assessment prior to and after FDG-PET. All patients reported subjective memory complaints. Patient A: 67-year-old female with swallowing difficulty. Patient B: 83-year-old male with decreased balance. Patient C: 77-year-old male with gait disturbance. Neuropsychological re-evaluations occurred at 64, 19, and 17months, respectively. Radiological interpretations of FDG-PET hypometabolism were reviewed. Clinically significant changes were defined as >1 standard deviation discrepancy from baseline performance. Patients A & C had predominant right hemisphere hypometabolism, and Patient B had predominantly left hemisphere hypometabolism. Patient A: hypometabolism for R > L frontoparietal, right temporal and occipital regions. Neuropsychological declines in left fine motor control/speed, attention, visual memory, and semantic fluency. Patient B: hypometabolism for left temporal, frontal, parietal, and occipital regions. Neuropsychological declines in semantic fluency and set-shifting. Patient C: hypometabolism for diffuse right hemisphere, including thalamus and basal ganglia. Neuropsychological declines in verbal learning and memory. There were no significant neuropsychological improvements for Patients A or C. Significant neuropsychological improvement for Patient B was evident for verbal memory and naming. The present case series highlights the diverse clinical presentation associated with CBD identified pathology on FDG-PET. Further studies are needed to characterize clinical phenotypes of CBD as they relate to quantitative FDG-PET pathology.

An integrated neuroimaging-omics approach for the gut-brain communication pathways in Alzheimer's disease.

A key role of the gut microbiota in the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease (AD), has been identified over the past decades. Increasing clinical and preclinical evidence implicates that there is bidirectional communication between the gut microbiota and the central nervous system (CNS), which is also known as the microbiota-gut-brain axis. Nevertheless, current knowledge on the interplay between gut microbiota and the brain remains largely unclear. One of the primary mediating factors by which the gut microbiota interacts with the host is peripheral metabolites, including blood or gut-derived metabolites. However, mechanistic knowledge about the effect of the microbiome and metabolome signaling on the brain is limited. Neuroimaging techniques, such as multi-modal magnetic resonance imaging (MRI), and fluorodeoxyglucose-positron emission tomography (FDG-PET), have the potential to directly elucidate brain structural and functional changes corresponding with alterations of the gut microbiota and peripheral metabolites in vivo. Employing a combination of gut microbiota, metabolome, and advanced neuroimaging techniques provides a future perspective in illustrating the microbiota-gut-brain pathway and further unveiling potential therapeutic targets for AD treatments.

FRI531 IgG4 Related Mass -forming Thyroid Disease: Two Case Reports

Abstract Disclosure: R.S. Braham: None. C. Droumaguet: None. M. Vitellius: None. J. Tran-van-nhieu: None. E. Béquignon: None. P. Desgranges: None. N. Limal: None. M. Mahevas: None. B. Godeau: None. IgG4 thyroiditis is an invasive fibrotic process involving the thyroid in a systemic disease. It is a rare inflammatory autoimmune disease with insidious presentation and nonspecific symptoms.We describe two unusual cases of mass forming IgG4 thyroiditis that were diagnosed recently in our department. The first case is about a 42-year-old woman who has a history of Hashimoto thyroiditis with hypothyroidism presenting with a rapid goiter growth, neck pain, dysphagia and hoarseness. A lymphoma was suspected. Ultrasonography shows heterogeneous hypoechoic lesions that may infiltrate the perithyroid muscles. Fine-needle aspiration (FNA) was suspicious of IgG4 infiltrative disease which was confirmed by microbiopsy. Only the thyroid was hypermetabolic on fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) Scan. No improvement under corticosteroid treatment and Rituximab. Surgery was planified to relieve pressure symptoms. The thyroid surgery was very difficult because of the extensive fibrosis and only a biopsy was performed, confirming the diagnosis and excluding malignancy. The second case is about a 68-year-old woman with a history of hypertension and Graves disease presented with a neck right mass that was suspected to be a paraganglioma, hypermetabolic on FDG PET scan with no other localisation. This mass was surrounding the right primitive carotid artery, associated with thrombi of the internal jugular vein. FNA and microbiopsy found a fibrotic non specific tissue. Thyroidectomy and surgical biopsy of the neck mass were performed with histopathology confirming IgG4 disease on the thyroid gland with fibrosis. There were no hypocalcemia in the two cases and no other localisation. IgG4 related mass-forming thyroiditis is an extremely rare disease. It is now a recognizable pattern of IgG4 thyroiditis, and has as differential diagnosis Hashimoto’s thyroiditis, Graves disease and thyroidal carcinoma.We will discuss through these cases the different clinical presentation of this rare disease, the diagnostic tools, the treatment and the long term follow up. Presentation: Friday, June 16, 2023

SAT041 18F-FDG PET/CT Mapping Of Functional Microbial Niches To Understand Host Glucose Regulation After BCG Vaccinations

Abstract Disclosure: H. Dias: None. J.F. Fu: None. T.G. Luck: None. G.E. Wolfe: None. E. Hostetter: None. N.C. Ng: None. H. Zheng: None. W. Kühtreiber: None. J.C. Price: None. C. Catana: None. D.L. Faustman: None. Diverse microbiomes in humans are known to change host energy metabolism. When the bacillus Calmette-Guérin (BCG) vaccine, which consists of live but avirulent Mycobacterium bovis, is introduced as experimental therapy into human hosts with underlying type 1 diabetes (T1D), the BCG bacillus has been shown to gradually shift energy metabolism in host blood lymphoid cells from oxidative phosphorylation to aerobic glycolysis. Aerobic glycolysis draws more glucose out of the blood to fuel intracellular metabolism, and it may underlie the BCG bacillus’ therapeutic benefit: the systemic and long-term reduction of excess glucose from the blood of TID patients. The organ-specific niches where the BCG bacillus similarly alters metabolism and establishes persistent residence are not known. In a human clinical trial, we mapped the organ(s) niches for BCG-induced shift to aerobic glycolysis using fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and x-ray computed tomography (CT). This technique allowed us to reveal quantitatively, by Standardized Uptake Value Ratios, the organs with heightened glucose uptake in T1D participants (n=6) over a 2-year time-period after BCG vaccination versus before vaccination, as well as confirm earlier work that BCG vaccination gradually lowers blood sugar levels without any contribution from endogenous insulin. We also tested BALB/c mice (n=17) for the direct presence of BCG colonies in particular organ niches before and after vaccination. Results from both human and murine studies of the BCG microorganism concurred that the major anatomic site of functional metabolic change and residence is the spleen. The BCG bacillus also transiently mapped to the bone marrow, liver, circulating lymphocytes as in the descending aorta, and the lungs. Findings from human and murine studies support the spleen as the niche for the BCG vaccine’s functional improvement of metabolism. The spleen is significant because it is a lymphoid organ massive enough to explain BCG’s systemic benefit of lowering blood sugar to near normal levels in T1D. Presentation: Saturday, June 17, 2023

SAT562 Metastatic Oncocytic (Formerly Hürthle Cell) Thyroid Carcinoma in a Patient With Birt-Hogg-Dubé Syndrome

Abstract Disclosure: S. Vaid: None. R. Klein: None. P. Veeraraghavan: None. D.M. Blakaj: None. A. Agrawal: None. J. Sipos: None. S.I. Sherman: None. J. Klubo-Gwiezdzinska: None. S. Gubbi: None. Introduction: Birt-Hogg-Dubé syndrome (BHD) is a rare, autosomal dominant disorder due to a germline loss-of-function mutation in the folliculin (FLCN) gene. Clinical manifestations include pulmonary cysts, renal cell carcinoma, and skin tumors, while tumors of other sites such as thyroid are uncommon. Here, we report an extremely rare case of oncocytic thyroid carcinoma (OTC) in a patient with BHD. Clinical case: A 55-year-old male with BHD noted a lump in his neck which was identified as a 3 cm right thyroid nodule on sonogram. Medical history only included BHD, which was diagnosed based on the presence of pulmonary cysts and two family members with BHD. No family members had thyroid tumors, and the patient denied any history of radiation exposure. Fine needle aspiration biopsy was indeterminate (Bethesda III). A total thyroidectomy and central lymph node (LN) dissection was performed as LN metastases were identified on intraoperative frozen section. Histopathology revealed 3 foci of OTC, largest being 3.8 cm, with extrathyroidal extension into fibroadipose tissue, 3/31 LN metastases with the largest deposit of 0.5 cm without extranodal extension. A 156.6 mCi dose of I-131 radioiodine (RAI) was administered. No uptake was noted on the post-therapy scan. Four months later, new right lateral cervical lymphadenopathy was noted on computed tomogram (CT). A right lateral selective neck dissection was performed, which identified 3/28 metastatic LNs without extranodal extension. Next generation gene sequencing testing of the metastatic tumor revealed the pathogenic FLCN (H429fs*27) variant, along with TP53 (R248Q), and DAXX (L666fs*29) pathogenic variants. Over the next 20 months, serum thyroglobulin increased from 1.8 ng/ml to 121 ng/mL (normal: 1.6 - 59.9 ng/mL). Several sub-centimeter lung nodules and new right cervical lymphadenopathy were noted on CT, and these lesions demonstrated increased uptake on fluorodeoxyglucose positron emission tomography (PET/CT) and on Ga-68 DOTATATE PET/CT scans. Due to close proximity to the right internal jugular vein, the cervical lymphadenopathy was deemed to be inoperable. Stereotactic radiation was administered to the neck, which resulted in substantial shrinkage of the neck metastases. The patient continues to be on active surveillance, with tyrosine kinase inhibitors or peptide receptor radionuclide therapy being potential future systemic therapy options in case of disease progression. Conclusion: Thyroid tumors have been occasionally reported in BHD. While most of them are papillary or follicular tumors, only one case of OTC in BHD has been previously reported in the literature [1]. This report underscores the importance of screening for thyroid neoplasms in patients with BHD. Reference: 1. Panagiotidis et al. World J Nucl Med. 2018;17(2):123-125 Presentation Date: Saturday, June 17, 2023

Avelumab treatment for patients with metastatic Merkel cell carcinoma can be safely stopped after 1 year and a PET/CT-confirmed complete response.

Immune checkpoint inhibitor treatment of patients with metastatic Merkel cell carcinoma (mMCC) has shown high response rates, ranging from 33% to 73%. The ideal duration of treatment, however, is currently unknown. The aim of this study was to evaluate if avelumab treatment for mMCC can be safely stopped after 1year of treatment and a complete response (CR) confirmed by fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) imaging. Patients who receivedmore than one dose of avelumab treatment for mMCC between November 2017 and February 2022 were included in this study. Treatment was discontinued in case of a FDG-PET/CT confirmed CR after 1year (26 cycles) of avelumab or a CR and unacceptable toxicity earlier. The primary end point was recurrence-free survival (RFS). Sixty-five patients were included: 25 (38%) had a FDG-PET/CT-confirmed CR at discontinuation of avelumab. In those 25 patients, reasons for discontinuation of treatment were completion of 1year of treatment in 13 (52%), toxicity in five (20%), and patient preference in seven (28%). Median duration of treatment in this group was 11months (interquartile range, 6.1-11.7). Median follow-up was 27months (interquartile range, 15.8-33.8). The 12-month RFS was 88% (95% CI, 0.74-1) and median RFS was not reached. Two patients (8%) had a recurrence at 4 and 7months after discontinuation of treatment. Patients with mMCC who acquire a CR on PET/CT imaging appear to have durable responses after discontinuation of treatment after 1 year.

Role of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in evaluation of newly diagnosed breast cancer patients

Role of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in evaluation of newly diagnosed breast cancer patients

Multimodality Appearances of Marginal Zone Lymphoma Masquerading as Cryptogenic Organizing Pneumonia-serial Chest Radiograph and High-resolution Computed Tomography Appearances: (18F) Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Staging Utility.

Marginal zone lymphoma (MZL) is a group of low-grade, indolent, non-Hodgkin lymphomas rarely manifesting in the lungs. A 46-year-old man presenting with shortness of breath and cough was investigated and treated over 10 months for an atypical pattern of lung disease in keeping with cryptogenic organizing pneumonia (COP). Initial lung biopsies were nondiagnostic - repeat sampling eventually showed MZL. Staging whole-body (18F) fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) demonstrated multisystem stage IV disease with intensely avid widespread pulmonary changes resembling COP. The case elegantly illustrates that pulmonary MZL can present insidiously masquerading as COP and shows the value of (18F) FDG PET/CT to stage extranodal MZL.

Extensive Pulmonary Cryptococcosis as a Presentation in an Immunocompetent Young Male: A Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Finding.

A 42-year-old male presented with a dry cough, breathlessness, and fever. He underwent a computed tomography that revealed large consolidation in the right lung. Biopsy revealed Cryptococcus neoformans. He was on antifungal for 4 months with no clinicoradiological improvement. 18F- fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) showed consolidations in the right lung with multiple lung nodules. 18F-FDG PET/CT ascertains the diagnosis of residual fungal infection and rules out extrapulmonary involvement.