Abnormal Uptake Research Articles

S2490 Discovery of Gastric Adenocarcinoma During PEG Tube Placement in Patient With Epiglottic Squamous Cell Carcinoma

Introduction: Multiple primary neoplasms constitute up to 2-17% of cancer diagnoses. Etiological factors such as genetics, lifestyle choices, and immune status have a significant impact on the likelihood of patients developing synchronous multiple primary tumors. The timing of diagnosis for the different cancers has a major impact on disease management, treatment plans, and patient outcomes. We report a patient who was diagnosed with gastric adenocarcinoma at the time of percutaneous endoscopic gastrostomy (PEG) tube placement for dysphagia secondary to squamous cell carcinoma of the anterior epiglottis. Case Description/Methods: A 77-year-old male presented to the outpatient surgery center for upper endoscopy with PEG tube placement. Two months prior, the patient was diagnosed with p16 negative invasive squamous cell carcinoma of the anterior epiglottis. He was referred for PEG tube placement for nutrition supplementation due to 5 months of progressive dysphagia and protein calorie malnutrition with an unintentional weight loss of 50 lbs. Past social history was significant for tobacco dependence with 52 pack years and alcohol dependence. At the time of PEG tube placement, endoscopy revealed a 1.5 cm excavated lesion at the gastric incisura. Biopsy was performed to rule out malignancy. PEG tube was successfully placed. The gastric biopsy was consistent with diffuse type signet ring gastric adenocarcinoma. PET scan 1 month prior to PEG tube placement did not show any foci of abnormal FDG uptake outside of the primary lesion in the epiglottis. Patient is currently undergoing treatment for laryngeal carcinoma with chemotherapy and radiation. Assessment and treatment for gastric cancer diagnosis will be deferred until completion of treatment for laryngeal carcinoma (Figure). Discussion: Concurrent laryngeal and gastric cancer is a unique diagnosis that has not been well reported in the literature. However, given the strong association for both malignancies with chronic alcohol and tobacco use, it is not unreasonable for both to occur in the same patient in an independent manner. The literature has shown that signet ring cell carcinomas have significantly lower 18F-FDG uptake than other forms of gastric cancer. These findings highlight the importance of completing a full endoscopic evaluation in all patients undergoing endoscopy even for procedures as straightforward as PEG tube placement.Figure 1.: Esophagogastroduodenoscopy showing gastric adenocarcinoma at the gastric incisura.

S3488 Symptomatic Meckel’s Diverticulum in an Adult Presenting With Recurrent Gastrointestinal Bleeding

Introduction: Meckel’s diverticulum is a gastrointestinal congenital malformation that results due to persistence of the vitelline duct, and is commonly diagnosed in children before the age of two. Rarely, symptomatic Meckel’s diverticulum can present in adults, as in this case with recurrent gastrointestinal bleeding. Case Description/Methods: A 51-year-old male with a history of iron deficiency anemia presented to the hospital with hematochezia associated with mild epigastric tenderness. He had a similar presentation one year ago with unrevealing EGD, colonoscopy, and video capsule endoscopy. Three months ago, repeat colonoscopy was notable for a single nonbleeding diverticulum in the terminal ileum and outpatient double balloon endoscopy was recommended, however not yet done due to current hospitalization. He presented with tachycardia and hypotension as well as a hemoglobin 10.6g/dL (previously 11.4g/dL few weeks prior) and mildly elevated BUN. CT abdomen and pelvis was negative for any active bleeding. Repeat EGD and colonoscopy was unremarkable except for blood-tinged fluid interspersed in the colon but again the source of bleeding remained obscure. Given the history of a previous finding of a terminal ileum diverticulum and persistence of hematochezia, a Meckel’s scan was performed revealing abnormal uptake in the right mid to lower abdomen suspicious for Meckel’s diverticulum containing ectopic gastric mucosa. Patient was taken to the operation room; a large Meckel’s diverticulum was noted at approximately two feet proximal to the ileo-cecal valve along with hemorrhagic inflammatory changes within the local mesentery. Patient underwent partial small bowel resection and appendectomy with pathology revealing a Meckel’s diverticulum of the ileum with gastric heterotopia. Patient had an uncomplicated recovery postoperatively along with resolution of hematochezia. Discussion: A finding of Meckel’s diverticulum is common in the pediatric population; however, it is a rare diagnosis in adults. This case highlights the importance of considering Meckel’s diverticulum for instances of recurrent gastrointestinal bleeding, especially in patients who are still symptomatic despite an extensive workup. It is also important to notice that Meckel's diverticulum can be missed on video capsule study.

A Visual Interpretation Algorithm for Assessing Brain Tauopathy with 18F-MK-6240 PET.

In vivo characterization of pathologic deposition of tau protein in the human brain by PET imaging is a promising tool in drug development trials of Alzheimer disease (AD). 6-(fluoro-18F)-3-(1H-pyrrolo[2,3-c]pyridin-1-yl)isoquinolin-5-amine (18F-MK-6240) is a radiotracer with high selectivity and subnanomolar affinity for neurofibrillary tangles that shows favorable nonspecific brain penetration and excellent kinetic properties. The purpose of the present investigation was to develop a visual assessment method that provides both an overall assessment of brain tauopathy and regional characterization of abnormal tau deposition. Methods: 18F-MK-6240 scans from 102 participants (including cognitively normal volunteers and patients with AD or other neurodegenerative disorders) were reviewed by an expert nuclear medicine physician masked to each participant's diagnosis to identify common patterns of brain uptake. This initial visual read method was field-tested in a separate, nonoverlapping cohort of 102 participants, with 2 additional naïve readers trained on the method. Visual read outcomes were compared with semiquantitative assessments using volume-of-interest SUV ratio. Results: For the visual read, the readers assessed 8 gray-matter regions per hemisphere as negative (no abnormal uptake) or positive (1%-25% of the region involved, 25%-75% involvement, or >75% involvement) and then characterized the tau binding pattern as positive or negative for evidence of tau and, if positive, whether brain uptake was in an AD pattern. The readers demonstrated agreement 94% of the time for overall positivity or negativity. Concordance on the determination of regional binary outcomes (negative or positive) showed agreement of 74.3% and a Fleiss κ of 0.912. Using clinical diagnosis as the ground truth, the readers demonstrated a sensitivity of 73%-79% and specificity of 91%-93%, with a combined reader-concordance sensitivity of 80% and specificity of 93%. The average SUV ratio in cortical regions showed a robust correlation with visually derived ratings of regional involvement (r = 0.73, P < 0.0001). Conclusion: We developed a visual read algorithm for 18F-MK-6240 PET offering determination of both scan positivity and the regional degree of cortical involvement. These cross-sectional results show strong interreader concordance on both binary and regional assessments of tau deposition, as well as good sensitivity and excellent specificity supporting use as a tool for clinical trials.

Abbreviated Molecular Breast Imaging: Feasibility and Future Considerations.

Molecular breast imaging (MBI) is a supplemental screening modality consistently demonstrating incremental cancer detection over mammography alone; however, its lengthy duration may limit widespread utilization. The study purpose was to assess feasibility of an abbreviated MBI protocol, providing readers with mediolateral oblique (MLO) projections only and assessing performance in lesion detection and localization. Retrospective IRB-exempt blinded reader study administered to 5 fellowship-trained breast imaging radiologists. Independent reads performed for 124 screening MBI cases, half abnormal and half negative/normal. Readers determined whether an abnormality was present, side of abnormality, and location of abnormality (medial/lateral). Abnormal cases had confirmatory biopsy or surgical pathology; normal cases had imaging follow-up ensuring true negative results. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to assess performance. A false negative result indicated that a reader failed to detect abnormal uptake; a false positive result indicated a reader incorrectly called an abnormality for a negative case. Tests for association included chi-square, Fisher-exact, and analysis of variance. Mean reader performance for detecting abnormal uptake: sensitivity 96.8%, specificity 98.7%, PPV 98.8%, and NPV 96.9%. Accuracy in localizing lesions to the medial or lateral breast was 100%. There were no associations in reader performance with reader experience, reader technique, lesion morphology, or lesion pathology. Median lesion size was 1.0 cm (range: 0.4-8.0 cm). All readers correctly identified 97.7% (42/43) of lesions with malignant or elevated risk pathology. An abbreviated MBI protocol (MLO images only) maintained high accuracy in lesion detection and localization.

A GATA-type transcription factor SreA affects manganese susceptibility by regulating the expression of iron uptake-related genes

SreA has been identified as a GATA-type transcription factor that represses iron uptake to avoid iron excess during iron sufficiency. However, knowledge about whether SreA also affects the homeostasis of other divalent metal ions is limited. In this study, by screening Aspergillus fumigatus transcription factor deletion mutant libraries, we demonstrate that the sreA deletion mutant shows the greatest tolerance to MnCl2 among the tested divalent metal ions. Fe and Mn stimuli are able to enhance the expression of SreA with the different time-dependent manner, while the expression of SreA contributes to Mn2+ tolerance. Lack of SreA results in abnormally increased expression of a series of siderophore biosynthesis genes and iron transport-related genes, especially under MnCl2 treatment. Further mechanistic exploration indicated that lack of SreA exacerbates abnormal iron uptake, and iron excess inhibits cellular Mn content; thus, deletion of sreA results in Mn tolerance. Thus, findings in this study have demonstrated a new unexplored function for the transcription factor SreA in regulation of the Mn2+ tolerance.

68Ga-DOTATATE PET/CT Incidentally Detects Relapsed Chronic Lymphocytic Leukemia in Patient With Metastatic Neuroendocrine Tumor.

A 54-year-old man with metastatic well-differentiated neuroendocrine tumor of the pancreas underwent 68Ga-DOTATATE PET/CT scan to evaluate treatment response. Patient was known for remote history of chronic lymphocytic leukemia (CLL), previously treated. Scan revealed diffusely increased abnormal tracer uptake throughout the marrow of the axial and proximal appendicular skeleton. Bone marrow biopsy revealed relapsed CLL. We present a rare case of relapsed CLL incidentally detected on 68Ga-DOTATATE PET/CT.

Lhermitte-Duclos Disease Related With Cowden Syndrome Mimicking Metastatic Lung Cancer on FDG PET/CT.

Cowden syndrome is characterized by multiple hamartomatous and neoplastic lesions including Lhermitte-Duclos disease, which is the main criterion for the diagnosis. Herein, we presented a patient with suspected metastatic disease referred to PET/CT, which showed mildly hypermetabolic multinodular thyroid goiter, multiple hamartomatous pulmonary, and breast nodules. Also, intense hypermetabolism was noted on the cerebellar tumor lesion. Lhermitte-Duclos disease was diagnosed based on the characteristic MRI findings, and she was followed up with a diagnosis of Cowden syndrome. Our case indicates that Cowden syndrome should be included as a differential diagnosis of abnormal FDG uptake in the multiple systemic hamartomatous tumors.

A progressive and refractory case of breast cancer with Cowden syndrome

BackgroundCowden syndrome is a rare autosomal-dominant disease with a high risk of malignant tumors of the breast, commonly caused by germline mutations in the PTEN gene. Most breast cancers related to Cowden syndrome showed typically a slow-growing and favorable clinical course. Here, we report a progressive case of triple-negative breast cancer in a patient who was diagnosed with Cowden syndrome.Case presentationA 35-year-old female with breast cancer was referred to our hospital. Histopathological examination of the tumor showed that it was triple-negative breast cancer with high proliferation marker. Preoperative positron emission tomography-computed tomography showed abnormal uptake in the left cerebellar hemisphere in addition to the right breast and axillary lymph node. Brain T2-weighted magnetic resonance imaging revealed hyperintense bands in the left cerebellar hemisphere lesion, which demonstrated a “tiger-stripe” appearance. The patient’s mother had died of endometrial cancer. Subsequently, she underwent genetic testing, leading to a diagnosis of Cowden syndrome with a pathogenic variant c.823_840del.18 at exon 8 in PTEN. She was treated with neoadjuvant chemotherapy of eribulin and cyclophosphamide followed by adriamycin and cyclophosphamide. However, her tumors increased after these treatments. She was immediately surgically treated and received adjuvant chemotherapy of capecitabine. Unfortunately, the cancer recurred in the lung nine months after surgery. We then administered paclitaxel and bevacizumab therapy, but the disease rapidly progressed. Consequently, the patient died due to breast cancer about three months after recurrence.ConclusionWe report an aggressive case of cancer with Cowden syndrome which was resistant to standard chemotherapy. Alteration of the phosphatidylinositol-3 kinase/Akt/mammalian target of rapamycin pathway due to inactivating PTEN protein may be associated with chemoresistance and serves as a candidate for therapeutic intervention in PTEN-related cancers.

Gastric heterotopia in the ileum mimicking Meckel's diverticulum

Gastric heterotopia is the presence of normal gastric tissue elsewhere than the stomach. It has been reported in the alimentary tract from oropharynx to rectum. It is common in esophagus, duodenum, and in congenital anomalies such as Meckel's diverticulum (MD) and duplications, however it is rarely found in the small intestine beyond the ligament of Treitz without the accompanying anomalies. In this presentation, we report a 3-year-old female with chronic anemia and abnormal uptake in technetium99 pertechnetate scintigraphy in right lower quadrant of abdomen which lead to diagnosis of ectopic gastric tissue in ileum, outside of the MD. • Heterotopic gastric mucosa can be a probable cause for consumptive anemia in children. • Ectopic gastric tissue occurring in sites other than Meckel's diverticulum can mislead the diagnosis regarding the Technetium 99 m pertechnetate scintigraphy or Meckel's scan. • If ectopic gastric tissue is not found in Meckel’s diverticulum, a search in other parts of small intestine is recommended.

The mechanisms of ferroptosis and its role in alzheimer's disease.

Alzheimer’s disease (AD) accounts for two-thirds of all dementia cases, affecting 50 million people worldwide. Only four of the more than 100 AD drugs developed thus far have successfully improved AD symptoms. Furthermore, these improvements are only temporary, as no treatment can stop or reverse AD progression. A growing number of recent studies have demonstrated that iron-dependent programmed cell death, known as ferroptosis, contributes to AD-mediated nerve cell death. The ferroptosis pathways within nerve cells include iron homeostasis regulation, cystine/glutamate (Glu) reverse transporter (system xc−), glutathione (GSH)/glutathione peroxidase 4 (GPX4), and lipid peroxidation. In the regulation pathway of AD iron homeostasis, abnormal iron uptake, excretion and storage in nerve cells lead to increased intracellular free iron and Fenton reactions. Furthermore, decreased Glu transporter expression leads to Glu accumulation outside nerve cells, resulting in the inhibition of the system xc− pathway. GSH depletion causes abnormalities in GPX4, leading to excessive accumulation of lipid peroxides. Alterations in these specific pathways and amino acid metabolism eventually lead to ferroptosis. This review explores the connection between AD and the ferroptosis signaling pathways and amino acid metabolism, potentially informing future AD diagnosis and treatment methodologies.

Real-World Testing of a Machine Learning-Derived Visual Scale for Tc99m TRODAT-1 for Diagnosing Lewy Body Disease: Comparison with a Traditional Approach Using Semiquantification.

Objectives: Abnormal dopamine transporter (DAT) uptake is an important biomarker for diagnosing Lewy body disease (LBD), including Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). We evaluated a machine learning-derived visual scale (ML-VS) for Tc99m TRODAT-1 from one center and compared it with the striatal/background ratio (SBR) using semiquantification for diagnosing LBD in two other centers. Patients and Methods: This was a retrospective analysis of data from a history-based computerized dementia diagnostic system. MT-VS and SBR among normal controls (NCs) and patients with PD, PD with dementia (PDD), DLB, or Alzheimer’s disease (AD) were compared. Results: We included 715 individuals, including 122 NCs, 286 patients with PD, 40 with AD, 179 with DLB, and 88 with PDD. Compared with NCs, patients with PD exhibited a significantly higher prevalence of abnormal DAT uptake using all methods. Compared with the AD group, PDD and DLB groups exhibited a significantly higher prevalence of abnormal DAT uptake using all methods. The distribution of ML-VS was significantly different between PD and NC, DLB and AD, and PDD and AD groups (all p < 0.001). The correlation coefficient of ML-VS/SBR in all participants was 0.679. Conclusions: The ML-VS designed in one center is useful for differentiating PD from NC, DLB from AD, and PDD from AD in other centers. Its correlation with traditional approaches using different scanning machines is also acceptable. Future studies should develop models using data pools from multiple centers for increasing diagnostic accuracy.

Atypical Alzheimer's disease phenotypes with normal or borderline PET biomarker profiles.

Posterior cortical atrophy (PCA) and logopenic progressive aphasia (LPA) are clinical syndromes that commonly have underlying Alzheimer's disease (AD), although non-AD pathologies have also been reported. PET imaging allows for identification of beta-amyloid (Aβ) and tau in AD, so we aimed to assess these in a large cohort to identify patients that do not have evidence for biomarker-defined AD. Eight-one patients, 47 PCA and 34 LPA, underwent extensive neurological and neuropsychological testing, [11C] Pittsburgh compound B, [18F] flortaucipir and [18F] fluorodeoxyglucose PETs. Global Aβ and tau-PET standardized uptake value ratios (SUVRs) were plotted for all patients and outliers, and patients with abnormally low SUVRs compared to the biomarker-classic cohort were identified. Six (7.4%) biomarker-outlier cases were identified, and three patterns were observed: (i) negative/borderline Aβ-PET and striking widespread tau-PET uptake (two LPA); (ii) negative/borderline Aβ-PET and low tau-PET uptake (three PCA) and (iii) elevated Aβ-PET uptake but mild focal tau-PET uptake (one LPA). Among the unusual patients in group ii, two patients showed no abnormal tau uptake suggesting non-AD pathology, with one developing features of cortico-basal syndrome and the other dementia with Lewy bodies. The remaining patient showed very mild focal tau uptake. This study demonstrates that a small minority (~ 8%) of PCA and LPA patients do not show the typical striking patterns of Aβ and tau PET uptake, with only 2% showing absence of both proteins. These findings will help inform the use of molecular PET in clinical treatment trials that include patients with atypical phenotypes of AD.

Incidental Findings on 18 F-Fluorocholine PET/CT for Parathyroid Imaging.

Introduction 18 F-choline positron emission tomography/computed tomography (PET/CT) is an upcoming imaging technique for the localization of hyperfunctioning parathyroid glands. However, 18 F-choline is a nonspecific tracer that also accumulates in malignancies, inflammatory lesions, and several other benign abnormalities. The aim of this study was to determine the occurrence and relevance of incidental findings on 18 F-choline PET/CT for parathyroid localization. Materials and Methods 18 F-choline PET/CTs performed in our center for parathyroid localization from 2015 to 2019 were reviewed. Abnormal uptake of 18 F-choline, with or without anatomical substrate on the co-registered low-dose CT and also incidental findings on CT without increased 18 F-choline uptake were recorded. Each finding was correlated with follow-up data from the electronic medical records. Results A total of 388 18 F-choline PET/CTs were reviewed, with 247 incidental findings detected in 226 patients (58%): 82 18 F-choline positive findings with corresponding pathology on CT, 16 without CT substrate, and 149 18 F-choline negative abnormalities on CT. Malignant lesions were detected in 10/388 patients (2.6%). Of all 98 detected 18 F-choline positive lesions, 15 were malignant (15.3%), concerning 4 metastases and 11 primary malignancies: breast carcinoma ( n = 7), lung carcinoma ( n = 2), thyroid carcinoma ( n = 1), and skin melanoma ( n = 1). Conclusion Clinically relevant incidental findings were observed in a substantial number of patients. In 15.3% of the incidental 18 F-choline positive findings, the lesions were malignant. These data contribute to better knowledge of 18 F-choline distribution, enhance interpretation of 18 F-choline PET/CT, and guide follow-up of incidental findings. Attention should especially be paid to breast lesions in this particular patient group with hyperparathyroidism in which women are typically over-represented.

99mTc-Vitamin C SPECT/CT imaging in SARS-CoV-2 associated pneumonia.

We present the first 99mTc-Vitamin C single-photon emission computed tomography/computed tomography (SPECT/CT) images obtained in patients with SARS-CoV-2 (COVID-19) infection. The CT portion of SPECT/CT images showed mostly peripheral patchy and ground-glass opacities in both lungs, which are consistent with a diagnosis of SARS-CoV-2-associated pneumonia in both patients. 99mTc-Vitamin C SPECT images showed increased tracer uptake corresponding to abnormal lung findings seen on CT in patient 1 who was newly diagnosed and treatment naïve. However, no abnormal uptake corresponding to lung CT findings was seen in patient 2 who received anti-SARS-CoV-2 treatment.

Standardized uptake values and attenuation correction in 18 F-sodium fluoride PET of the equine foot and fetlock.

Maximal standardized uptake values (SUVmax ) are commonly used for the interpretation of PET studies. Limited information regarding the SUVmax of 18 F-NaF PET in horses is currently available in the literature. The goals of this retrospective secondary analysis study were to provide reference values for 18 F-NaF SUVmax in the equine distal extremity and assess the effect of attenuation correction. Nonattenuation corrected (NAC) and CT-based attenuation corrected (CTAC) SUVmax were obtained from 19 feet and 19 fetlocks. Twenty regions of interest (ROIs) were defined for the foot and 22 for the fetlock. Areas presenting abnormal uptake were excluded. The overall NAC and CTAC SUVmax were 3.6 +/- 1.5 (mean +/- sd) and 5.0 +/- 1.8 for the feet and 2.9 +/- 1.1 and 3.8 +/- 1.4 for the fetlocks, respectively. The 3 ROIs showing the highest attenuation correction were the navicular center (83.4%), navicular flexor surface (74.9%) and distal phalanx flexor surface (81.3%), whereas attenuation correction was only 5.2% at the dorsal aspect of the proximal phalanx. Significant SUVmax differences were observed between the different ROIs (P<0.0001), with the toe (CTAC SUVmax 7.7 +/- 3.7), dorsal (7.5 +/- 1.9) and central (6.1 +/- 2.2) ROIs of the distal phalanx being significantly higher than those of the other areas. This study demonstrates that attenuation correction affects SUVmax in the equine distal extremity and should be performed if CT data are available. However, as the maximal attenuation correction results in less than doubling the signal intensity, nonattenuation corrected images likely remain relevant for subjective clinical interpretation.

Incremental Value of 18 F-FDG-Labeled Leukocytes PET/CT Over 18 F-FDG PET/CT Scan in the Detection of Occult Infection.

Differentiating infection and sterile inflammation is the main clinical concern of clinicians as they are closely related to each other. Although 18 F-FDG PET/CT imaging is widely used, its main disadvantage is its lack of specificity to discriminate aseptic from septic inflammation. 18 F-WBC PET/CT scan is a promising tool for the accurate diagnosis of infection owing to its high specificity. The aim of the present study is to determine the utility of 18 F-WBC PET/CT in the diagnosis of occult infections and to assess its incremental value over routine 18 F-FDG PET/CT scan. This prospective observational diagnostic accuracy study included 33 patients with fever of unknown origin or suspected periprosthetic infection and raised C-reactive protein and total leukocyte count. All the patients underwent both 18 F-WBC PET/CT scan and 18 F-FDG PET/CT scan using a standard protocol on 2 different days. Images of both the scans were evaluated by both visual analyses based on uptake intensity and quantitative grading based on lesion-to-background SUV max values. For interpretation of FDG PET/CT images, visual scoring of grade 0 (undetectable or no uptake), grade 1a (less than liver uptake), grade 1b (equivalent to liver uptake), grade 2 (higher than liver uptake), and grade 3 (higher than cerebellum uptake) was used. 18 F-WBC PET/CT images were also interpreted visually as grade 0 (undetectable or no uptake), grade 1a (significantly less than lumbar vertebrae or liver uptake for truncal lesions, and in case of extremity lesion slightly higher than neighboring soft tissue uptake or less than neighboring bone marrow uptake), grade 1b (equivalent to liver or lumbar vertebrae uptake for truncal lesions, and in case of extremity lesion significantly higher than neighboring soft tissue uptake or higher than neighboring bone marrow uptake), grade 2 (higher than liver or bone marrow uptake), and grade 3 (higher than twice the liver or bone marrow uptake). Similarly, a quantitative grading was also done based on lesion-to-background SUV max using a circular region of interest manually drawn. For both 18 F-FDG and 18 F-WBC PET/CT, the lesion-to-background ratio of <1.5 was recorded as grade 0, 1.5-2.5 as grade 1a, 2.5-3.5 as grade 1b, 3.5-4.5 as grade 2, and >4.5 as grade 3. Final diagnosis was made by histopathological, microbiological analysis, or clinical-radiological workup. Twenty-nine foci of suspected infection were found in 25/33 patients by either 18 F-FDG PET/CT or 18 F-WBC PET/CT scan. No abnormal uptake of either 18 F-FDG or 18 F-FDG WBC scan was seen in 8 patients. There was a concordance of 18 F-FDG PET/CT and 18 F-WBC PET/CT in 28 sites each using grade 1b of visual and quantitative analysis, respectively. Of the 29 suspicious infected foci, 18 were proven positive for infection (14/18 sites by the histopathological/microbiological culture and the rest 4/18 sites by clinical/radiological workup). Culture of aspirates or biopsy from 11/29 suspicious sites was proven noninfective. Seven of 11 suspicious sites were proven noninfective by clinical/radiological workup. The mean clinical follow-up was 8 months (1-15 months).Overall significantly higher diagnostic accuracy was demonstrated with 18 F-WBC PET/CT in comparison to 18 F-FDG PET/CT for the detection of infection ( P < 0.05). The highest diagnostic accuracy of 18 F-WBC PET/CT scan was reported with both grade 1b of visual as well as of quantitative analysis (lesion-to-background SUV max , 2.5-3.5) and grade 2 for both visual and quantitative analysis for 18 F FDG PET/CT. 18 F-WBC PET/CT has a higher diagnostic accuracy over 18 F-FDG PET/CT for the diagnosis of occult infection.

Corticomedullary Mixed Tumor of the Adrenal Gland with Apparent 18F-Fluorodeoxyglucose Activity But No 68GA-DOTATATE Uptake on Positron Emission Tomography/Computed Tomography.

Corticomedullary mixed tumor (CMT) is a single adrenal tumor mass composed histologically by an admixture of adrenal cortical and medullary cells. It is a rare condition, with approximately 20 cases reported to date. To our knowledge, the positron emission tomography (PET) imaging findings of this mostly benign tumor have not been reported in the literature. We present a case of CMT who was evaluated with both 18F-fluorodeoxyglucose (18F-FDG) and 68Ga-DOTATATE. The hypermetabolic tumor seen on 18F-FDG PET/computed tomography scan showed no abnormal uptake by 68Ga-DOTATATE.

False-Positive Findings on Bone Scintigraphy after MRI-Guided Stereotactic Ablative Radiotherapy for Osseous Oligometastasis

Radical radiation therapy for oligorecurrent prostate cancer is considered to improve both overall and disease-specific survival. Therefore, accurate diagnosis by imaging is important when considering the indications for radiation therapy. We present a case of marginal recurrence of bone metastases from castrationresistant prostate cancer previously treated with radical radiation therapy, which could not be detected by bone single photon emission computed tomography/ computed tomography (SPECT/CT) but could be diagnosed by 68Ga-prostate-specific membrane antigen positron emission tomography/computed tomography (68Ga-PSMA PET/CT). Bone SPECT/CT showed false-positive tracer uptake in the lesion previously irradiated. 68Ga-PSMA PET/CT scan showed no abnormal uptake in the previously irradiated lesion, but showed intense uptake in the newly developed metastasis near the irradiated site. 68Ga-PSMA PET/CT scan may be able to diagnose marginal recurrence after radiation therapy more accurately than bone SPECT/CT

Abstract 3343: Durable response to osimertinib monotherapy as first line treatment in stage IVB lung adenocarcinoma with atypical EGFR L747P mutation

Abstract Background: Targeted therapy plays a critical role in NSCLC with a certain type of mutation. Osimertinib is a third generation EGFR tylosine kinase inhibitor (TKI) which is primarily indicated for NSCLC with EGFR exon 19 deletions or exon 21 L858R mutations. Although use of osimertinib is currently limited to patients with common EGFR mutations, it has been reported that patients with NSCLC harboring uncommon EGFR mutations demonstrated response to EGFR TKIs. Herein, we present a case of advanced adenocarcinoma of the lung with atypical EGFR L747P mutation that revealed a noteworthy durable response to osimertinib monotherapy as first line treatment. Case presentation: A 47-year-old woman with no smoking history presented with new-onset hemoptysis and cough. A chest CT scan showed a lobulated, spiculated 38 mm left upper lung mass with innumerable bilateral pulmonary nodules. CT-guided biopsy demonstrated adenocarcinoma of lung with PD-L1 1-2%. Subsequent PET-CT scan revealed hypermetabolic neoplasm in the left lower lobe with scattered area of abnormal focal FDG uptake within the liver. Brain MRI showed unremarkable findings. The patient was diagnosed with stage IVB adenocarcinoma of lung with multiple hepatic metastases. Circulating tumor DNA (ctDNA) NGS assay showed EGFR L747P [0.3% of variant allele frequency (VAF)] and tissue NGS assay revealed EGFR L747P missense variant c.2239_2240delinsCC (22.8% of VAF). The patient was started on osimertinib 80 mg daily. Follow up CT scan in six week demonstrated decrease in size of the left lower lobe lung mass to 32 mm. She has maintained durable SD for six months without any adverse effects. Most recent follow-up CT scan after eight months from the treatment demonstrated SD of the mass in the left lower lobe and less prominent numerous pulmonary nodules. Discussion: It has not been reported that osimertinib monotherapy is used as first line therapy in NSCLC with EGFR L747P mutation. We report the case of durable response to osimertinib in patients with advanced NSCLC with EGFR L747P mutation. Our case highlights the potential efficacy of osimertinib to NSCLC with atypical EGFR mutation. Although there was a clinical trial to explore clinical activity of osimertinib in patients with NSCLC harboring uncommon EGFR mutation, EGFR L747R mutation was not investigated at that time. To date, there are no ongoing clinical trials on the use of osimertinib in NSCLC with EGFR L747P mutation. Further investigations are warranted to confirm the efficacy of osimertinib in this type of mutation. Citation Format: Horyun Choi, Yeun Ho Lee, Jinah Kim, Leeseul Kim, Na Hyun Kim, Young Kwang Chae. Durable response to osimertinib monotherapy as first line treatment in stage IVB lung adenocarcinoma with atypical EGFR L747P mutation [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 3343.

Prognostic Value of Hybrid PET/MR Imaging in Patients with Differentiated Thyroid Cancer.

Simple SummaryHybrid positron emission tomography (PET)/magnetic resonance (MR) is an emerging imaging modality with great potential to provide complementary data acquired at the same time, under the same physiological conditions. We evaluated the prognostic value of hybrid 18F-fluorodeoxyglucose (FDG) PET/MR in patients with differentiated thyroid cancer (DTC) who underwent total thyroidectomy and radioactive iodine therapy for suspicion of disease relapse. Our findings suggest that hybrid PET/MR imaging may have the potential to improve the information content of one modality with the other and would offer new opportunities in patients with DTC. However, there is need of more clinical studies to understand the additional value of 18F-FDG PET/MR in patients with DTC.Background: Hybrid positron emission tomography (PET)/magnetic resonance (MR) is an emerging imaging modality with great potential to provide complementary data acquired at the same time, under the same physiological conditions. The aim of this study was to evaluate the prognostic value of hybrid 18F-fluorodeoxyglucose (FDG) PET/MR in patients with differentiated thyroid cancer (DTC) who underwent total thyroidectomy and radioactive iodine therapy for suspicion of disease relapse. Methods: Between November 2015 and February 2017, 55 patients underwent hybrid 18F-FDG PET/MR. Assessment of positive MR was made considering all sequences in terms of malignancy based on the morphological T2-weighted features and the presence of restricted diffusivity on diffusion-weighted imaging images and both needed to be positive on the same lesion. Both foci with abnormal 18F-FDG uptake, which corresponded to tissue abnormalities on the MR, and tracer accumulation, which did not correspond to normal morphological structures, were considered positive. Results: During follow-up (mean 42 ± 27 months), 29 patients (53%) had disease recurrence. In the Cox univariate regression analysis age, serum Tg level ≥ 2 ng/mL, positive short tau inversion recovery (STIR), and positive PET were significant predictors of DTC recurrence. Kaplan–Meier survival analyses showed that patients with Tg ≥ 2 ng/mL had poorer outcomes compared to those with serum Tg level < 2 ng/mL (p < 0.05). Similarly, patients with positive STIR and positive PET had a worst outcome compared to those with negative STIR (p < 0.05) and negative PET (p < 0.005). Survival analysis performed in the subgroup of 36 subjects with Tg level ≥ 2 ng/mL revealed that patients with positive PET had a worst outcome compared to those with negative PET (p < 0.05). Conclusions: Age, serum Tg level ≥ 2 ng/mL, positive STIR, and positive 18F-FDG PET were significant predictors of DTC recurrence. However, the serum Tg level was the only independent predictor of DTC. Hybrid PET/MR imaging may have the potential to improve the information content of one modality with the other and would offer new opportunities in patients with DTC. Thus, further studies in a larger patient population are needed to understand the additional value of 18F-FDG PET/MR in patients with DTC.