False-Negative 68Ga-FAPI PET/CT in Pediatric Thyroid Medullary Carcinoma Seen With 68Ga-DOTATOC PET/CT and 18F-FDG PET/CT.

ABSTRACT: In adults, 68Ga-FAP inhibitor (68Ga-FAPI) PET/CT outperforms 68Ga-radiolabeled somatostatin analog peptides (68Ga PET/CT) and 18F-FDG PET/CT in detecting thyroid lesions. This is the case of a 13-year-old boy newly diagnosed with medullary thyroid cancer with high calcitonin level. 68Ga PET/CT revealed the presence of only a primary thyroid lesion. Proven to be superior in detecting metastasis, 68Ga-FAPI PET/CT was performed. The results came out negative for primary and potential metastatic lesions. This case sheds shed light on false-negatives reported in 68Ga-FAPI PET/CT scans in pediatric patients, emphasizing the need for alternate radiotracers when a negative study is met.

Diagnostic Performance of FDG-PET/CT Scan as Compared to US-Guided FNA in Prediction of Axillary Lymph Node Involvement in Breast Cancer Patients.

PURPOSE: The aim of this study was to evaluate the diagnostic ability of 2-deoxy-2-[fluorine-18]fluoro-d-glucose (18F-FDG) PET/non-contrast CT compared with those of ultrasound (US)-guided fine needle aspiration (FNA) for axillary lymph node (ALN) staging in breast cancer patients. PATIENTS AND METHODS: Preoperative 18F-FDG PET/non-contrast CT was performed in 268 women with breast cancer, as well as ALN dissection or sentinel lymph node (SLN) biopsy. One hundred sixty-four patients underwent US-guided FNA in combination with 18F-FDG PET/CT. The diagnostic performance of each modality was evaluated using histopathologic assessments as the reference standard. The receiver operating characteristic (ROC) curves were compared to evaluate the diagnostic ability of several imaging modalities. RESULTS: Axillary 18F-FDG uptake was positive in 180 patients, and 125 patients had axillary metastases according to the final pathology obtained by ALN dissection and/or SLN dissection. Of the patients with positive 18F-FDG uptake in the axilla, 21% had false-positive results, whereas 79% were truly positive. Eighty-eight patients had negative 18F-FDG uptake in the axilla, among which 25% were false-negative. 18F-FDG-PET/CT had a sensitivity of 86.59% and a specificity of 63.46% in the assessment of ALN metastasis; on the other hand, US-guided FNA had a sensitivity of 91.67% and a specificity of 87.50%. The mean primary cancer size (p = 0.04) and tumor grade (p = 0.04) in combination were the only factors associated with the accuracy of 18F-FDG PET/CT for detecting metastatic ALNs. CONCLUSION: The diagnostic performance of 18F-FDG PET/CT for the detection of axillary node metastasis in breast cancer patients was not significantly different from that of US-guided FNA. Combining 18F-FDG PET/CT with US-guided FNA or SLN biopsy could improve the diagnostic performance compared to 18F-FDG PET/CT alone.

Ictal and interictal FDG-PET in anti-NMDAR encephalitis with mutism.

We report a case of a 27-year-old right-handed gentleman with mutism and seizures diagnosed with Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis without evidence of underlying malignancy. Brain MRI was unremarkable. Clinical seizures were controlled but long-term video-EEG monitoring was needed for better characterization of his clinical manifestations especially that language partially improved. It was crucial to identify whether this mutism was ictal in origin or not. Ictal brain Positron Emission Tomography with 18 F-fluorodeoxyglucose (FDGPET) scan combined with EEG was done. It revealed left fronto-temporal, parietal, and crossed cerebellar hypermetabolism (or diaschisis) concomitant to the underlying rhythmic focal delta activity on EEG. Beside anti-epileptic drugs he was treated with escalating immunotherapy (intravenous solumedrol then immunoglobulins then full rituximab course). Six months later, EEG combined to FDG-PET scan were repeated, and were normal. At 3 years follow up the patient remains neurologically stable and seizure-free, off anti-epileptics drugs. Performing the FDGPET scan combined to EEG was useful to identify non-convulsive status epilepticus and should be performed early in anti-NMDAR encephalitis to guide treatment.

Early Sialadenitis After Radioactive Iodine Therapy for Differentiated Thyroid Cancer: Prevalence and Predictors.

INTRODUCTION: Sialadenitis is a frequent occurrence after radioactive iodine therapy (RAI). However, reports on its predictors and risk factors in the Eastern Mediterranean Region (EMRO) are scarce. AIM: This study aimed to identify risk factors for early sialadenitis in patients receiving RAI for differentiated thyroid cancer (DTC) at the American University of Beirut Medical Center. It also aimed to determine the prevalence and characteristics of such patients receiving RAI at our institution. METHODS: This was a retrospective study conducted at the American University of Beirut Medical Center. Medical charts were reviewed for all patients 18-79 years of age admitted to receive RAI for DTC between 01/01/2012 and 31/12/2015. Sialadenitis was deemed present if there were any records of neck swelling/pain, dry mouth, or difficulty swallowing within 48 hours of RAI administration. Characteristics between patients with sialadenitis and those without were compared to determine predictors. RESULTS: There were 174 patients admitted to receive RAI, predominantly females (71.3%), with papillary thyroid cancer (93.1%). The majority had lymph node involvement (64.5%). Pretreatment thyroid stimulating hormone (TSH) was greater than 75 mIU/ml in most patients (72.6%). The prevalence of sialadenitis was 20.1% (95% CI (15-27)). Being non-Lebanese and having a positive whole-body scan were associated with sialadenitis and persisted after adjustments (OR = 2.34 and 3.99). Non-Lebanese patients had higher rates of lymph nodes involvement (p value 0.005) and were kept off levothyroxine for longer periods (p value 0.02). CONCLUSION: The prevalence of sialadenitis at our institution was similar to other reported studies from the world. However, risk factors allude to more iodine exposure in the neck with positive whole-body scan uptake, lymph node involvement, and prolonged period of hypothyroidism.

Role of Early PET/CT Imaging with 68Ga-PSMA in Staging and Restaging of Prostate Cancer.

Ga-68 Prostate-Specific Membrane Antigen PET/CT is a new tool for the assessment of prostate cancer. Standard imaging time is 60 minutes post injection of radiotracer. At 60 minutes, there is physiologic accumulation of radiotracer in the urinary bladder which may cause some lesions in its vicinity to be obscured. Our aim is to determine if early imaging at 3 minutes in addition to standard imaging at 60 minutes can improve the detection of PSMA-avid lesions. A retrospective review of 167 consecutive patients was conducted. Overall, 115 patients (68.9%) were ruled to have prostate cancer based on imaging as seen on early or standard PET/CT images. In 106/115 (64%), the lesions were detected on both early and standard imaging; in 8/115 (6.9%), the lesions were only detected on early imaging; in 1/115 (0.6%) the lesion was detected only on standard imaging. The addition of early imaging significantly improved the overall detection rate of PSMA-avid lesions (p = 0.039). The ratio of patients with lesions detected on early imaging but not on standard imaging in restaging group was 7/88 and was higher than that in staging group 1/79 (p = 0.043). We recommend early imaging in addition to the standard imaging in Ga-68 PSMA PET/CT, particularly in patients presenting for restaging of prostate cancer.

Diagnostic performance of Gallium-68 prostate-specific membrane antigen positron emission tomography-computed tomography in intermediate and high risk prostate cancer.

Gallium-68 prostate-specific membrane antigen positron emission tomography-computed tomography (Ga-68 PSMA PET/CT) is an imaging modality that promises improved sensitivity and specificity of detection of prostate cancer lesions based on their increased uptake of PSMA-based radiotracers. It remains an emerging modality that has not yet been endorsed in the guidelines for the management of prostate cancer pending more established evidence to prove its efficacy. The objective of the study is to assess the value of Ga-68 PSMA PET/CT in the detection and localization of patients diagnosed with intermediate or high risk prostate cancer.Twenty three patients with intermediate or high risk prostate cancer had undergone Ga-68 PSMA PET/CT imaging prior to robotic assisted radical prostatectomy. Surgical specimens were then submitted for histological examinations. Lesions visualized on PET/CT and histology were independently mapped unto a 36-segment (Prostate Imaging Reporting and Data System version 2 [PI-RADS v.2]) map of the prostate. Concordance of visualization on PET/CT as compared to the histology as gold standard reference was then assessed. Lesions visualized on PET/CT and histology were independently mapped unto a 36-segment (PI-RADS v.2) map of the prostate. Concordance of visualization on PET/CT as compared to the histology as gold standard reference was then assessed.Sensitivity for all lesions identified on Ga-68 PSMA PET/CT was 42.37%; specificity was 88.61%. Both parameters were higher when considering only index lesions for which sensitivity was 68.42% and specificity was 98.23%. Sensitivity for the index lesions in intermediate risk group was 53.2% and was higher in the high risk group reaching 83.33%.Ga-68 PSMA PET/CT provides accurate localization of tumor lesions in patients with intermediate and high risk prostate cancer.

Case report of epithelioid osteoblastoma of the mandible: findings on positron emission tomography/computed tomography and review of the literature.

Epithelioid osteoblastoma is a clinically aggressive subtype of osteoblastoma that favors the mandible and the maxilla. Its histologic features lie on a spectrum between conventional osteoblastoma and low-grade osteosarcoma, thus making it difficult at times to confirm the diagnosis. It is known to have a high risk of recurrence after surgical resection, but it is a benign entity and does not have the propensity to metastasize. To our knowledge, there are no published reports on findings of epithelioid osteoblastoma on positron emission tomography/computed tomography (PET/CT). We report a case of a 25-year-old male patient with a diagnosis of epithelioid osteoblastoma of the mandible. The lesion exhibited significantly increased fluorodeoxyglucose uptake on PET/CT with a maximum standardized uptake value of 5.5. PET/CT is not specific in differentiating between malignant and benign bone lesions but may be necessary to rule out distant lesions when a confirmed diagnosis of epithelioid osteoblastoma cannot be obtained through histologic examination.