68 Ga-DOTATATE PET to Characterize Lesions in the Neuroaxis.

AIM: The differentiation of paragangliomas, schwannomas, meningiomas, and other neuroaxis tumors in the head and neck remains difficult when conventional MRI is inconclusive. This study assesses the utility of 68 Ga-DOTATATE PET/CT as an adjunct to hone the diagnosis. PATIENTS AND METHODS: This retrospective study considered 70 neuroaxis lesions in 52 patients with 68 Ga-DOTATATE PET/CT examinations; 22 lesions (31%) had pathologic confirmation. Lesions were grouped based on pathological diagnosis and best radiologic diagnosis when pathology was not available. Wilcoxon rank sum tests were used to test for differences in SUV max among paragangliomas, schwannomas, and meningiomas. Receiver operator characteristic curves were constructed. RESULTS: Paragangliomas had a significantly greater 68 Ga-DOTATATE uptake (median SUV max , 62; interquartile range [IQR], 89) than nonparagangliomas. Schwannomas had near-zero 68 Ga-DOTATATE uptake (median SUV max , 2; IQR, 1). Intermediate 68 Ga-DOTATATE uptake was seen for meningiomas (median SUV max , 19; IQR, 6) and other neuroaxis lesions (median SUV max , 7; IQR, 9). Receiver operator characteristic analysis demonstrated an area under the curve of 0.87 for paragangliomas versus all other lesions and 0.97 for schwannomas versus all other lesions. CONCLUSIONS: Marked 68 Ga-DOTATATE uptake (>50 SUV max ) favors a diagnosis of paraganglioma, although paragangliomas exhibit a wide variability of uptake. Low to moderate level 68 Ga-DOTATATE uptake is nonspecific and may represent diverse pathophysiology including paraganglioma, meningioma, and other neuroaxis tumors but essentially excludes schwannomas, which exhibited virtually no uptake.

Perfusion-only imaging in pregnant women: A comparative reader study with implications for practice patterns.

This study seeks to understand the value of ventilation imaging in pregnant patients imaged for suspected pulmonary embolism (PE). Ventilation-perfusion (VQ) scans in this high-risk population were compared to ventilation-only scans. We hypothesize that in this relatively healthy population, the exclusion of ventilation scans will not impact the rate of scans interpreted as positive. This retrospective blinded comparative reader study on collated VQ scans performed on pregnant patients in the course of routine clinical care in a > 5 year period (03/2012 to 07/2017). Each set of VQ and perfusion only (Q) studies were reviewed by 8 readers (4 nuclear radiology fellows and 4 nuclear medicine faculty) in random order; the Q scans simply omitted the ventilation images. Readers recorded each study as PE, no PE, or non-diagnostic (prospective investigative study of acute PE diagnosis classifications). Logistic mixed effects models were used to test the association between scan type (VQ vs Q). 203 pairs of studies in 197 patients were included (6 patients had 2 scans). Subjects ranged from 14 to 45 years of age, with a median 28 years. A significant association between scan type and positive/negative classification. Q-scans received more positive classifications than VQ-scans (median of 7.6% vs 6.7%). No association was seen between scan type and positive/indeterminate classification, nor between scan type and negative/indeterminate classification. The exclusion of ventilation images in VQ-scans was associated with a higher rate of positive studies, but this difference was small (<1%). Given the overwhelmingly normal percentage of Q-exams (>90% in our study), and the benefits of omitting ventilation imaging, perfusion-only imaging should be considered a reasonable option for imaging the pregnant patient to exclude PE.

18F-Fluciclovine PET/CT in Therapeutic Decision Making for Prostate Cancer: A Large Single-Center Practice-Based Analysis.

METHODS: We carried out a retrospective cohort study of patients with BR after primary treatment of PC who received imaging with 18F-fluciclovine PET/CT at our institution between January 2010 and January 2019. PET/CT results were compared with biopsy, conventional imaging results, and/or response to PC therapy. 18F-Fluciclovine PET/CT performance statistics and effects on treatment planning were calculated. RESULTS: A total of 328 patients with a median age of 71 years (range, 47-90 years) and median serum prostate-specific antigen level of 1.6 ng/mL (0.02-186.7 ng/mL) were included. Three hundred thirty-six 18F-fluciclovine PET/CT scans were analyzed and classified as positive (65%), negative (25%), or equivocal (10%) based on radiology reports. Sensitivity was 93% (95% confidence interval, 86%-96%) and specificity was 63% (95% confidence interval, 45%-77%). Of patients with known management recommendations post-PET/CT, scan results changed or influenced pre-PET/CT management plans in 73%, and 58% of recommendations involved treatment modality decisions. Overall, 82% of patients' actual management was concordant with post-PET/CT recommendations. Of evaluable patients, 116 (35%) had some form of post-PET radiotherapy included in their care plans, with 95% receiving radiotherapy at a PET-avid target. CONCLUSIONS: In the largest single-institutional cohort to date, 18F-fluciclovine PET/CT showed value in the workup of PC in the setting of BR, with noteworthy influence over clinical management decisions. Further studies are needed to evaluate whether PET/CT-based changes in management are associated with improved outcomes.

Update on Quantitative Imaging for Predicting and Assessing Response in Oncology.

Molecular imaging has revolutionized clinical oncology by imaging-specific facets of cancer biology. Through noninvasive measurements of tumor physiology, targeted radiotracers can serve as biomarkers for disease characterization, prognosis, response assessment, and predicting long-term response/survival. In turn, these imaging biomarkers can be utilized to tailor therapeutic regimens to tumor biology. In this article, we review biomarker applications for response assessment and predicting long-term outcomes. 18F-fluorodeoxyglucose (FDG), a measure of cellular glucose metabolism, is discussed in the context of lymphoma and breast and lung cancer. FDG has gained widespread clinical acceptance and has been integrated into the routine clinical care of several malignancies, most notably lymphoma. The novel radiotracers 16α-18F-fluoro-17ß-estradiol and 18F-fluorothymidine are reviewed in application to the early prediction of response assessment of breast cancer. Through illustrative examples, we explore current and future applications of molecular imaging biomarkers in the advancement of precision medicine.