Diagnostic Accuracy of 99mTc-Sestamibi SPECT/CT for Characterization of Solid Renal Masses.

Our objective was to assess the diagnostic accuracy of 99mTc-sestamibi SPECT/CT for characterizing solid renal masses. Methods: Imaging and clinical records of patients who underwent 99mTc-sestamibi SPECT/CT for clinical work-up of their solid renal masses from September 2018 to October 2021 were retrospectively reviewed. Histopathology formed the reference standard, and the diagnoses were categorized as malignant/concerning (renal cell carcinomas [RCCs] other than chromophobe histology) and benign/nonconcerning (oncocytic tumors including chromophobe RCC, other benign diagnoses) to calculate the sensitivity and specificity of 99mTc-sestamibi SPECT/CT and contrast-enhanced CT (ceCT). The clinical reads of the SPECT/CT images were used for visual classification of the lesions. Additionally, the SPECT images were manually segmented to obtain the maximum and mean counts of the lesion and adjacent renal cortex and maximum and mean lesion Hounsfield units. Results: 99mTc-sestamibi SPECT/CT was performed on 42 patients with 62 renal masses. A histopathologic diagnosis was available for 27 patients (18 male, 9 female) with 36 solid renal masses. ceCT findings were available for 20 of these patients. The most commonly identified single histologic type was clear cell RCC (13/36; 36.1%). Oncocytic tumors were the most common group of nonconcerning lesions (15/36), with oncocytoma as the predominant histologic type (n = 6). The sensitivity and specificity of SPECT/CT for diagnosing a nonconcerning lesion were 66.7% and 89.5%, respectively, compared with 10% and 75%, respectively, for ceCT. The lesion-to-kidney ratios for maximum and mean counts and maximum lesion Hounsfield units showed significant differences between the 2 groups (P < 0.05). The lesion-to-kidney mean count ratio at a cutoff of 0.46 showed a sensitivity and specificity of 87.5% and 86.67%, respectively, for detecting nonconcerning lesions, which was significantly higher than that of ceCT. Conclusion: The current literature on the utility of 99mTc-sestamibi SPECT/CT for characterization of solid renal masses is limited. We offer additional evidence of the incremental value of 99mTc-sestamibi SPECT/CT over ceCT for differentiating malignant or aggressive renal tumors from benign or indolent ones, thereby potentially avoiding overtreatment and its associated complications. Quantitative assessment can further increase the diagnostic accuracy of SPECT/CT and may be used in conjunction with visual interpretation.

Adverse Clinical Events at the Injection Site Are Exceedingly Rare After Reported Radiopharmaceutical Extravasation in Patients Undergoing 99mTc-MDP Whole-Body Bone Scintigraphy: A 12-Year Experience.

The deleterious effects of high-dose radiation on normal tissue are sometimes extrapolated to diagnostic (SPECT and PET) radiopharmaceutical extravasation (RPE). It has been hypothesized that diagnostic RPE can have gradually evolving local tissue injury and a potentially increased risk of local dermatologic or oncologic diseases over a longer period. However, data on clinical adverse events after diagnostic RPE are limited. Therefore, our primary aim was to study the occurrence of short-term and long-term clinical adverse events in patients who underwent 99mTc-methylene diphosphonate (99mTc-MDP) whole-body bone scintigraphy (WBBS) with reported RPE. Methods: The records of 99mTc-MDP WBBS performed from June 2010 to January 2022 were retrospectively examined for RPE documented in the scan reports. The clinical records of patients with a documented RPE were extensively reviewed for any related short-term adverse events (within 2 wk of the WBBS: local symptoms and care sought for local dermatologic or musculoskeletal issues) and long-term adverse events (until the last follow-up: local deleterious effects and related consults for dermatology, plastic surgery, oncology, or orthopedics). Results: Retrospective review of the records of 31,679 99mTc-MDP WBBS studies showed RPE documented in 118 (0.37%). Medical records were not retrievable for 22 patients, yielding a final cohort of 96 patients with reported RPE. The median follow-up was 18.9 mo (interquartile range, 7.8-45.7 mo). Short-term events were noted in 4 patients, of whom one was asymptomatic. Of the 3 symptomatic patients, 2 experienced mild discomfort at the injection site, and 1 had tender swelling. Three of the 4 events were in patients who had a prior intravenous contrast extravasation for contrast-enhanced CT performed earlier during the day and a 99mTc-MDP injection later at the same site, likely leading to RPE. None of the long-term local events had any plausible link with the RPE event. Conclusion: Reported RPE was rare, and 3 patients (0.009%) had short-term local symptoms, all of which were likely related to the prior higher-volume intravenous contrast extravasation. The smaller-volume diagnostic radiopharmaceutical injections for WBBS are highly unlikely to cause local symptoms on their own. No patient had any long-term adverse event with a plausible link to the RPE.

Detection of Additional Primary Neoplasms on 18F-Fluciclovine PET/CT in Patients with Primary Prostate Cancer.

The aim of this study was to evaluate the detection rate of incidental second primary neoplasms in patients with prostate cancer on 18F-fluciclovine PET/CT. Methods: Imaging reports and patient demographic data were retrospectively reviewed from 663 clinical 18F-fluciclovine PET/CT studies, performed in 601 patients for the assessment of their prostate cancer (643 - recurrence evaluation, 20 - initial staging) from August 2016 to April 2021. Maximum SUV (SUVmax) of the suspected second neoplasms was determined. The results of 18F-fluciclovine PET/CT were correlated with clinical and radiologic studies to determine the nature of the suspected second neoplasms. Results: Fifty-five patients (9.1%) had findings suggestive of a second neoplasm. Thirty-nine of 55 had a known second neoplasm diagnosed before the PET/CT. An incidental second primary neoplasm was first suspected on 18F-fluciclovine PET/CT in 16 of 601 patients (2.7%). Three of the 16 patients had PET/CT suggestive of a meningioma that was corroborated on MRI. Of the remaining 13 patients, 11 had a tissue diagnosis confirming a malignancy. Second malignancies included renal cell carcinoma (RCC; 5/11; 45.5%), urothelial carcinoma (n = 2), multiple myeloma, chondrosarcoma, cutaneous squamous cell carcinoma, and squamous cell carcinoma of the esophagus and lung (n = 1, each; except for 1 patient with both esophageal and lung carcinomas). Among histopathologically confirmed malignancies, clear-cell RCC had the lowest uptake (SUVmax 3.4), and cutaneous squamous cell carcinoma had the highest uptake (SUVmax 13.6). Of the 2 patients with no histopathologic confirmation, 1 had ultrasound and MRI findings corroborating the diagnosis of RCC. The other patient had a solitary lung nodule suggestive of primary lung carcinoma and elected to undergo observation. Conclusion: Incidental findings consistent with a second primary neoplasm are not infrequently seen on 18F-fluciclovine PET/CT performed for assessment of prostate cancer (9.1%). Of the incidentally detected primary cancers, RCC was the most common (45.5%). These findings indicate the need for a careful analysis of 18F-fluciclovine PET/CT images, due to the broad tumor imaging capabilities of this radiotracer.