11C-Choline PET/CT for Detection and Localization of Parathyroid Adenomas.

OBJECTIVE: The purpose of this study is to determine the efficacy of 11C-choline PET/CT for the detection of parathyroid adenomas by retrospectively reviewing a large patient population. MATERIALS AND METHODS: In this single-institution retrospective study, 7088 11C-choline PET/CT scans performed of 2933 men with prostate cancer from January 2005 through February 2016 were evaluated. Patients with suspected parathyroid adenomas were identified through a review of the electronic medical record and relevant imaging. Patient demographics, laboratory results, and lesion characteristics were noted. Pathologically proven parathyroid adenomas and lesions in patients with imaging or laboratory findings consistent with the diagnosis were considered positive. RESULTS: Thirteen men (mean [± SD] age, 72 ± 7 years) with pathologically or laboratory-proven parathyroid adenomas were identified. All had abnormally elevated serum calcium and parathyroid hormone levels. All adenomas were tracer avid on 11C-choline PET/CT (maximum standardized uptake value, 5.6 ± 3.0), with activity averaging 4.2 times that of the blood pool and 2.1 times that of the adjacent thyroid. One case of an ectopic adenoma was identified. Of the six pathologically confirmed cases, none displayed high-grade features such as capsular, vascular, or adjacent tissue invasion. Three additional patients with possible parathyroid adenomas at 11C-choline PET/CT were ultimately found to have thyroid lesions on the basis of tissue diagnosis; however, none of these patients had abnormal calcium or parathyroid hormone levels. CONCLUSION: In our patient population, 11C-choline PET/CT identified parathyroid adenomas with high specificity. Prospective investigation is warranted to validate this result and delineate the utility of 11C-choline PET/CT relative to other modalities.

Clinical Outcomes of Radioactive Iodine Redifferentiation Therapy in Previously Iodine Refractory Differentiated Thyroid Cancers.

Objective: Redifferentiation therapy (RDT) can restore radioactive iodine (RAI) uptake in differentiated thyroid cancer (DTC) cells to enable salvage 131I therapy for previously RAI refractory (RAIR) disease. This study evaluated the clinical outcomes of patients who underwent RDT and identified clinicopathologic characteristics predictive of RAI restoration following RDT. Methods: This is a retrospective case series of 33 patients with response evaluation criteria in solid tumors (RECIST)-progressive metastatic RAIR-DTC who underwent RDT between 2017 and 2022 at the Mayo Clinic (Rochester, MN). All patients underwent genomic profiling and received MEK, RET or ALK inhibitors alone, or combination BRAF-MEK inhibitors for 4 weeks. At week 3, those with increased RAI avidity in metastatic foci received high-dose 131I therapy. Baseline and clinicopathologic outcomes were comprehensively reviewed. Results: Of the 33 patients, 57.6% had restored RAI uptake following RDT (Redifferentiated subgroup). 42.1% (8/19) with papillary thyroid cancers (PTC), 100% (4/4) with invasive encapsulated follicular variant PTCs (IEFV-PTCs), and 100% (7/7) with follicular thyroid cancers (FTC) redifferentiated. All (11/11) RAS mutant tumors redifferentiated compared with 38.9% (7/18) with BRAF mutant disease (6 PTC and 1 IEFV-PTC). 76.5% (13/17) of redifferentiated and 66.7% (8/12) of non-redifferentiated patients achieved a best overall RECIST response of stable disease (SD) or non-complete response/non-progressive disease. Both subgroups had a median 12% tumor shrinkage at 3 weeks on drug(s) alone. The redifferentiated subgroup, following high-dose 131I therapy, achieved an additional median 20% tumor reduction at 6 months after RDT. There were no statistically significant differences between both groups in progression free survival (PFS), time to initiation of systemic therapy, and time to any additional therapy. Of the entire cohort, 6.1% (2/33) experienced histologic transformation to anaplastic thyroid cancer, 15.1% (5/33) died, and all had redifferentiated following RDT and received 131I therapy. Conclusion: RDT has the potential to restore RAI avidity and induce RECIST responses following 131I therapy in select patients with RAIR-DTC, particularly those with RAS-driven "follicular" phenotypes. In patients with PTC, none of the evaluated clinical outcomes differed statistically between the redifferentiated and non-redifferentiated subgroups. Further studies are needed to better characterize the long-term survival and/or safety outcomes of high-dose RAI following RDT, particularly whether it could be associated with histologic anaplastic transformation.

123I Scan With Whole-Body Retention Measurement at 48 Hours for Simplified Dosimetry Before 131I Treatment of Metastatic Thyroid Cancer.

ABSTRACT: A previously published model (Atkins) allows for calculation of 131I maximum tolerated activity on the basis of 48-hour whole-body retention of 131I on a pretherapy diagnostic scan. Our practice uses iodine 123I for diagnostic imaging of metastatic thyroid cancer for staging before 131I therapy, with images typically acquired 24 hours after administration of the radiopharmaceutical. We explored the feasibility of an additional 123I whole-body scan and retention measurement at 48 hours, with application of the model to estimate maximum tolerated activity of radioiodine before 131I treatment of metastatic thyroid cancer.

The value of [(18)F]fluorodeoxyglucose positron emission tomography/computed tomography in extranodal natural killer/T-cell lymphoma.

PURPOSE: To our knowledge, there are no published data pertinent to the use of [(18F)]fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in patients with natural killer (NK)/T-cell lymphoma. The purpose of this study was to assess the value of FDG PET/CT in this aggressive type of non-Hodgkin lymphoma. PATIENTS AND METHODS: All patients with NK/T-cell lymphoma referred for FDG PET/CT at our institution from July 2001 to July 2006 were retrospectively studied. PET/CT examinations were blindly reviewed by 2 experienced readers. The results were compared with the status of the disease, which was determined after evaluation of biopsy, laboratory, clinical and conventional imaging examination, and follow-up results. PET/CT results were thereby classified as true-positive, true-negative, false-positive, or false-negative. The degree of FDG uptake in the positive lesions was semiquantified using maximum standard uptake value (SUV(max)). RESULTS: Twenty-one PET/CT examinations were performed in 10 patients with NK/T-cell lymphoma. For nasal disease, PET/CT was true-positive in 5 cases, true-negative in 15 cases, and positive but unconfirmed in 1 case. For extranasal disease, PET/CT was true-positive in 3 cases, true-negative in 16 cases, and false-negative in 2 cases. The mean SUV(max) in PET-positive lesions in nasal cavities or paranasal sinuses was 16 gm/mL (range, 5-25 gm/mL; median, 19.3 gm/mL). In extranasal disease, the mean SUV(max) was 10.9 gm/mL (range, 4.6-34.1 gm/mL; median, 5.6 gm/mL). CONCLUSION: Viable NK/T-cell lymphoma is intensely FDG hypermetabolic. PET/CT appears to be sensitive for the detection of disease in the nasopharynx and, to a lesser extent, in extranasal sites.

Nuclear medicine gastrointestinal bleeding examination utilizing an UltraTag kit reveals unusual bone marrow and hepatic uptake: a case study report.

In vitro gastrointestinal (GI) bleed testing such as the UltraTag kits has been successfully used for a number of years. None of the research studies identified reported any significant bone marrow and liver uptake. An 80-y-old male patient was admitted to the hospital for rectal bleeding. An initial GI bleed study using the UltraTag kit was normal. Two days later, a second GI bleed scan was performed while the patient was undergoing blood transfusion with packed red blood cells. The technologist withdrew a blood sample from the blood transfusion bag. The second GI bleed test demonstrated unusual liver and bone marrow uptake. We believe that this liver uptake might have been caused by the labeling of fragmented red blood cells or oxidation of pertechnetate in the form of technetium dioxide.

Cohort study on radioactive iodine-induced hypothyroidism: implications for Graves' ophthalmopathy and optimal timing for thyroid hormone assessment.

BACKGROUND: Graves' ophthalmopathy (GO) develops or worsens in up to one-third of patients treated with radioactive iodine (RAI) for Graves' hyperthyroidism. We sought to identify the prevalence of development or worsening of GO in patients treated with RAI for Graves' hyperthyroidism and to identify the risk factors associated with that outcome. METHODS: We identified a retrospective cohort of consecutive patients treated with RAI at Mayo Clinic (Rochester, MN) between 2005 and 2006. We assessed their medical records for evidence of hypothyroidism and development or worsening of GO in the year after therapy. Hypothyroidism was defined as thyrotropin >3.0 mIU/L or free thyroxine <0.8 ng/dL. RESULTS: We identified 291 consecutive patients who received RAI therapy during the study period, with 195 out of 291 having complete follow-up data for a one-year period. GO was present in 46 out of 195 patients (23.6%) at baseline. After RAI treatment, GO developed or worsened in 25 out of 195 patients (12.8%) and it was associated with hypothyroidism at first follow-up (p=0.011) with an odds ratio (OR) of 3.3 [95% confidence interval (CI) 1.3-8.7]. More smokers than nonsmokers developed new or worse GO (17.7% vs. 11.8%), but that difference did not reach statistical significance (p=0.35). Preexisting GO (24% of patients) was associated with a higher risk for negative GO outcome compared with patients who had no GO at baseline (11%; p=0.021). Both development of hypothyroidism by the first visit after RAI therapy (OR 3.6) and preexistent GO (OR 2.8) remained significant in a multivariate analysis. Development of hypothyroidism was more likely in patients with longer duration to first follow-up (p<0.001). By 6-8 weeks after RAI treatment, the prevalence of hypothyroidism was ∼40%, while that of hyperthyroidism was only 20%. CONCLUSIONS: The presence of hypothyroidism at the first assessment of thyroid function after RAI administration is a strong predictor for adverse GO outcome. This risk is highest in patients with preexisting GO. We suggest that in order to prevent clinical hypothyroidism and the associated risk for GO, the optimal time for first measurement of fT4 is before 6 weeks after RAI therapy.

18F-FDG PET and PET/CT in Burkitt's lymphoma.

OBJECTIVE: To explore the value of (18)F fluorodeoxy-glucose (FDG) positron emission tomography (PET) in Burkitt's lymphoma. METHODS: All Burkitt's lymphoma patients referred for FDG PET or FDG PET/computed tomography (CT) exams at our institution from June 2003 to June 2006 were included. Selected patients were followed and clinical information was reviewed retrospectively. Results from FDG PET-PET/CT, as blindly reviewed by a consensus of two experienced readers, were compared with the status of the disease as determined by other laboratory, clinical and imaging exams and clinical follow-up. FDG PET-PET/CT results were classified as true positive or negative and false positive or negative. The degree of FDG uptake in the positive lesions was semiquantified as maximum standard uptake value (SUVmax). RESULTS: Fifty-seven FDG PET-PET/CT exams were done in 15 patients. Seven exams were done for initial staging, 8 during and 14 after the completion of therapy, and 28 for disease surveillance. For nodal disease FDG PET-PET/CT was true positive in 8, true negative in 47 and false positive in 2 exams (sensitivity 100%, specificity 96%). For extranodal disease FDG PET-PET/CT was true positive in 6, true negative in 48 and false positive in 3 exams (sensitivity 100%, specificity 94%). The mean SUVmax for the positive nodal lesions was 15.7 (range 6.9-21.7, median 18.5) and for extranodal lesions was 14.2 (range 6.2-24.3, median 12.4). CONCLUSIONS: FDG PET-PET/CT is sensitive for the detection of viable disease in Burkitt's lymphoma. Affected areas demonstrated high degree of uptake that was reversible upon successful implementation of treatment.