Effect of hormonal therapy on 18F-fluciclovine PET/CT in the detection of prostate cancer recurrence, localization of metastatic disease, and correlation with prostate-specific antigen.

INTRODUCTION: 18F-Fluciclovine, is a positron emission tomography (PET) radiotracer approved for the localization of sites of prostate cancer recurrence in men with a rising prostate-specific antigen (PSA) after definitive treatment. To explore the impact of androgen deprivation therapy (ADT) on the performance of 18F-fluciclovine, we conducted a retrospective analysis to compare the 18F-fluciclovine PET/CT positivity rate in patients receiving ADT at the time of the scan with the rate achieved in patients not receiving ADT. METHODS: A retrospective review of data from patients who underwent 18F-fluciclovine PET/CT for biochemical recurrence of prostate cancer between December 2016 to March 2020 was performed. The cohort was divided into an ADT group (patient reportedly on ADT) and a non-ADT group (not currently receiving ADT). Patients with unknown ADT status or undetectable/unknown PSA were excluded. For each group, the number of positive 18F-fluciclovine PET/CT scans (positivity rate) was evaluated for the whole body, prostate/bed, and extraprostatic regions and rates were correlated with PSA. The Fisher's Exact test was applied to establish the significance between the ADT and non-ADT positivity groups. Mantel-Haenszel trend test was performed to assess linearity between the positivity rate and PSA level. RESULTS: In 320 patients, the status of ADT was known. At the time of the 18F-fluciclovine scan, 68/320 (21%) patients were on ADT, while 252/320 (79%) were not. The median Gleason score was 8 (range of 6-10) in the ADT group vs. 7 (range of 6-10) in the non-ADT group (P < 0.001). Overall, positivity rates demonstrated no statistical significance between the ADT and non-ADT groups; Positivity rates (ADT vs. non-ADT) were 82% (56/68) vs. 82% (206/252) for the whole body, 57% (39/68) vs. 60% (152/252) for prostate/bed, and 60% (41/68) vs. 53% (133/252) for extraprostatic regions (P > 0.05). A positive linear correlation was noted between PSA and each group's positivity rate (P < 0.01). However, no significant difference was observed between ADT and non-ADT groups at different PSA levels (P > 0.05). CONCLUSIONS: Detection of prostate cancer recurrence with 18F-fluciclovine PET/CT is not significantly influenced by ADT, suggesting that localization of disease in patients with detectable PSA who are receiving ADT is feasible with 18F-fluciclovine.

Positivity Rate of [18F]Fluciclovine PET/CT in Patients with Suspected Prostate Cancer Recurrence at PSA Levels Below 1 ng/mL.

PURPOSE: Early and precise localization of recurrent prostate cancer lesions after local therapy facilitates optimal disease management. Here, we present results from a single-center study to evaluate the utility of [18F]fluciclovine PET/CT to localize prostate cancer recurrence in patients with PSA <1 ng/mL. PROCEDURES: Data from men who underwent [18F]fluciclovine PET/CT (August 2016-March 2020) for suspected recurrent prostate cancer and who had a PSA value <1ng/mL were retrospectively reviewed. The number of positive scans (positivity rates, PR) was calculated for the whole body, prostate/bed, and extraprostatic regions (pelvic or extrapelvic lymph nodes, bones, and soft tissue). PR were stratified by pre-scan PSA. RESULTS: Data from 113 patients were included. In total, 98 (87%) were post-prostatectomy and 15 (13%) had received non-surgical primary therapy. Twenty patients (18%) were receiving ADT at the time of the scan, 91 (81%) were not, and ADT status was not known for 2 (1.8%) patients. The overall PR at PSA <1ng/mL was 59% (67/113). For the prostate/bed, it was 35% (40/113), and for extraprostatic locations, it was 37% (42/113). At PSA >0-<0.2, 0.2-<0.5, and 0.5-<1 ng/mL, the overall PR was 43% (10/23), 70% (35/50), and 55% (22/40), respectively. In the prostate/bed, these were 13% (3/23), 50% (25/50), and 30% (12/40), respectively, and in extraprostatic lesions were 30% (7/23), 44% (22/50), and 33% (13/40), respectively. Pelvic lymph nodes were the most common site for extraprostatic lesions (29/113, 26%). PR in extrapelvic lymph nodes, bone, and soft tissue were 8.0%, 12%, and 3.5%, respectively. Soft tissue lesions comprised lung nodules (n=3) and a perirectal mass implant (n=1). CONCLUSIONS: Despite low PSA values, more than half of patients had positive [18F]fluciclovine PET/CT findings. Patients with low PSA levels may demonstrate suspicious findings outside of the pelvis, including abdominal lymph nodes and metastatic disease to bones and lungs.

Characterizing and Mitigating Bladder Radioactivity on 18F-Fluciclovine PET/CT.

18F-fluciclovine PET is approved for prostate cancer recurrence imaging. According to the radiopharmaceutical package insert, only 3% of the tracer is expected to be excreted in the urine over the first 4 h. Yet, in clinical practice we noticed a higher percentage of bladder excretion. We sought to evaluate and quantify early 18F-fluciclovine bladder radioactivity and determine whether refraining from voiding before 18F-fluciclovine injection would mitigate it. Methods: In total, 159 patients underwent 18F-fluciclovine PET/CT imaging as part of their clinical workup. The first 36 patients were instructed to void just before 18F-fluciclovine injection; the subsequent 123 patients were not asked to void. The SUVmax and SUVmean of the bladder, aorta, marrow, liver, and bladder volumes were determined. Comparing SUVmean of bladder to background, we characterized bladder radioactivity as insignificant (bladder < aorta), mild (bladder > aorta < marrow), moderate (bladder > marrow < liver), or intense (bladder > liver). Differences between the protocols were investigated. Results: Overall, 22% (35/159) of patients had moderate bladder activity and 8.8% (14/159) had intense bladder activity. A negative association was found between bladder volume and SUVmean A significant difference was found between the voiding and nonvoiding groups, with 38.9% (14/36) versus 17.1% (21/123) of patients, respectively, having moderate bladder activity and 22.2% (8/36) versus 4.9% (6/123) of patients, respectively, having intense bladder activity. Conclusion: Refraining from voiding before 18F-fluciclovine injection results in significantly lower urinary bladder radioactivity than does purposeful voiding before injection. We have modified our practice accordingly, particularly as moderate and intense bladder activity may mask or mimic local prostate cancer recurrence. Mechanisms underlying this phenomenon should be further investigated.

A Multimodal and Pathological Analysis of a Renal Cell Carcinoma Metastasis to the Thyroid Gland 11 Years Post Nephrectomy.

Thyroid lesions have a comprehensive differential diagnosis which include benign and malignant entities, such as metastases. However, metastases only account for a small percentage of thyroid lesions with renal cell carcinoma as the most common. Metastases to the thyroid pose a diagnostic dilemma as symptoms may not manifest for up to decades after removal of the renal cell carcinoma. Due to the nonspecific appearance on computed tomography and ultrasound, distinguishing metastases from primary thyroid malignancies is of the utmost importance for timely patient management. Our case demonstrates the importance of considering RCC metastases to the thyroid even years after nephrectomy to mitigate potential delays in diagnosis. We present the case of a 66-year-old male with a past medical history of renal cell carcinoma status post nephrectomy 11 years prior who demonstrated incidental thyroid abnormalities on positron emission tomography/computed tomography and ultrasound later confirmed as a metastasis of renal cell carcinoma.

Proof of Concept: Design and Initial Evaluation of a Device to Measure Gastrointestinal Transit Time.

Chronic constipation and gastrointestinal motility disorders constitute a large part of a gastroenterology practice and have a significant impact on a patient's quality of life and lifestyle. In most cases, medications are prescribed to alleviate symptoms without there being an objective measurement of response. Commonly used investigations of gastrointestinal transit times are currently limited to radiopaque markers or electronic capsules. Repeated use of these techniques is limited because of the radiation exposure and the significant cost of the devices. We present the proof of concept for a new device to measure gastrointestinal transit time using commonly available and inexpensive materials with only a small amount of radiotracer. Methods: We assembled gelatin capsules containing a 67Ga-citrate-radiolabeled grain of rice embedded in paraffin for use as a point-source transit device. It was tested for stability in vitro and subsequently was given orally to 4 healthy volunteers and 10 patients with constipation or diarrhea. Imaging was performed at regular intervals until the device was excreted. Results: The device remained intact and visible as a point source in all subjects until excretion. When used along with a diary of bowel movement times and dates, the device could determine the total transit time. The device could be visualized either alone or in combination with a barium small-bowel follow-through study or a gastric emptying study. Conclusion: The use of a point-source transit device for the determination of gastrointestinal transit time is a feasible alternative to other methods. The device is inexpensive and easy to assemble, requires only a small amount of radiotracer, and remains inert throughout the gastrointestinal tract, allowing for accurate determination of gastrointestinal transit time. Further investigation of the device is required to establish optimum imaging parameters and reference values. Measurements of gastrointestinal transit time may be useful in managing patients with dysmotility and in selecting the appropriate pharmaceutical treatment.

Managing Written Directives: A Software Solution to Streamline Workflow.

A written directive is required by the U.S. Nuclear Regulatory Commission for any use of 131I above 1.11 MBq (30 µCi) and for patients receiving radiopharmaceutical therapy. This requirement has also been adopted and must be enforced by the agreement states. As the introduction of new radiopharmaceuticals increases therapeutic options in nuclear medicine, time spent on regulatory paperwork also increases. The pressure of managing these time-consuming regulatory requirements may heighten the potential for inaccurate or incomplete directive data and subsequent regulatory violations. To improve on the paper-trail method of directive management, we created a software tool using a Health Insurance Portability and Accountability Act (HIPAA)-compliant database. This software allows for secure data-sharing among physicians, technologists, and managers while saving time, reducing errors, and eliminating the possibility of loss and duplication. Methods: The software tool was developed using Visual Basic, which is part of the Visual Studio development environment for the Windows platform. Patient data are deposited in an Access database on a local HIPAA-compliant secure server or hard disk. Once a working version had been developed, it was installed at our institution and used to manage directives. Updates and modifications of the software were released regularly until no more significant problems were found with its operation. Results: The software has been used at our institution for over 2 y and has reliably kept track of all directives. All physicians and technologists use the software daily and find it superior to paper directives. They can retrieve active directives at any stage of completion, as well as completed directives. Conclusion: We have developed a software solution for the management of written directives that streamlines and structures the departmental workflow. This solution saves time, centralizes the information for all staff to share, and decreases confusion about the creation, completion, filing, and retrieval of directives.