Dose-reduced [18F]PSMA-1007 PET is feasible for functional imaging of the renal cortex

Background In Prostate-specific membrane antigen (PSMA) positron emission tomography with computed tomography (PET-CT), there is significant renal uptake. The standard in renal cortical functional imaging is scintigraphy with technetium-99m labeled dimercaptosuccinic acid (DMSA). Using [68Ga]Ga-PSMA-11 PET for renal imaging has been suggested, but using [18F]PSMA-1007 has not been explored. The aims of this study were to establish the optimal time point for renal imaging after [18F]PSMA-1007 injection, to investigate the reproducibility of split renal uptake measurements, and to determine the margin for reduction in administered activity. Methods Twelve adult male patients with prostate cancer underwent [18F]PSMA-1007 PET-CT at 8 time points up to 5.5 h post-injection (p.i.). List-mode data were binned to durations of 10 to 120 s per bed position (bp). Left renal percentage of total renal uptake (LRU%) was measured, and the difference between highest and lowest measurement per patient (“delta max”) was calculated. Images acquired at 1 h, 2 h, and 5.5 h p.i. with durations of 10 to 120 s/bp were rated regarding image quality. Results Imaging at 2 h p.i. with 60 s/bp yielded acceptable quality in all cases. Increasing acquisition time to 15 min for a single bp would allow reducing administered activity to 0.27 MBq/kg, resulting in an effective dose of 0.4 mSv for a 1-year old child weighing 10 kg. The median delta max of LRU% measurements was 2.7% (range 1.8–7.3%). Conclusions Renal [18F]PSMA-1007 PET-CT is feasible, with imaging 2 h p.i., acceptable split renal uptake variability, and effective dose and acquisition time comparable to those of [99mTc]Tc-DMSA scintigraphy.

Blood Pressure and Glomerular Filtration Rate in Youth With Tuberous Sclerosis Complex

Background Renal involvement is very common in tuberous sclerosis complex (TSC) and is characterised by the development of angiomyolipoma and cysts. The aims of the present study were to assess kidney function and clinical features of renal involvement in TSC, including kidney function, and blood pressure (BP) levels in children, adolescents and young adults. Methods Non-selected patients with a definite diagnosis of TSC attending the paediatric neurology outpatient department of a tertiary hospital were included in a cross-sectional study. All participants had a renal imaging study within 6 months of ambulatory blood pressure (BP) and glomerular filtration rate (GFR) assessment. Data on demographics, history, genotype, kidney function at diagnosis and last imaging were collected. Results The median age of the patients was 15 years (IQR range 9 to18). 23.5% of the participants had ambulatory BP hypertension. Systolic BP levels correlated significantly with GFRDTPA values despite the absence of hyperfiltration. Greater increase in GFR from initial TSC diagnosis till the age of the assessment, resulted in higher GFR levels in childhood and adolescence in those that developed hypertension and possibly in those with angiomyolipoma or cysts. All patients with ambulatory BP hypertension had angiomyolipomas or cysts on renal imaging studies. Conclusions Hypertension may present with increased frequency in young patients with kidney disease associated with TSC. Routine ambulatory BP measurement could be part of the annual clinical assessment in patients with TSC.

SUN-713 Prevalence of Renal Cysts in Patients with Carney Complex

In the general population renal cysts appear most commonly in patients >50 y and in men. Among published studies, the prevalence of renal cysts detected by MRI was 27%, detected by CT was 20-41%, and detected by US was 4-17% (Mensel, et al., 2018; Choi, et al., 2016). In these studies, the male to female ratio in patients with renal cysts ranged from 1.4:1 to 2.93:1. Carney complex (CNC) is an autosomal dominant multiple endocrine neoplasia and lentiginosis syndrome predominantly caused by aberrant cAMP-protein kinase A (PKA) signaling mostly (but not always) due to germline inactivating defects in PRKAR1A which encodes the regulatory subunit type 1α of PKA. In a small retrospective study, 5 of 9 subjects with CNC had renal cysts on MRI or CT (Ye, et al., 2017). This same study evaluated the development of renal cysts in kidney-specific Prkar1a knockout mice, where all mice developed a renal cystic phenotype. To determine the prevalence of renal cysts, we performed a retrospective cohort study of patients with CNC evaluated at our institution between 1984 and 2019 who underwent renal imaging with MRI, CT, and/or US. We hypothesized that CNC leads to renal formation of cysts in humans, with increased number of renal cysts and earlier age at detection. 117 patients with CNC (69 female [59%], 48 male [41%]) were evaluated with renal imaging (56% MRI, 41% CT, 3% US). Of these, 39 (33%) patients had renal cysts that were first detected on imaging between the ages of 13 and 58 y (mean age at diagnosis 37.1 ±12.7 y; 5 [13%] 12-19 y, 5 [13%] 20-29 y, 10 [26%] 30-39 y, 11 [28%] 40-49 y, and 8 [21%] 50-59 y). The mean number of cysts was 1.3 ±0.7, and mean dominant cyst size was 1.2 ±0.9 cm. Average creatinine at diagnosis was 0.8 ±0.2 mg/dl. Of the patients with renal cysts, 22 were female (56% of patients with renal cysts, 32% of females with CNC that underwent renal imaging) and 17 were male (44% of patients with renal cysts, 35% of males with CNC that underwent renal imaging). There was no difference in the prevalence of renal cysts between males and females (35% vs 32%, p=.70, for a 1.1:1 ratio). Age, number, and dominant cyst size were also not different between sexes (p=.51, p=.84, and p=.26, respectively). However, creatinine levels were higher in males (0.9 ±0.1 vs 0.7 ±0.1, p<.001). All 39 patients with renal cysts had defects in PRKAR1A as compared to 73 of 78 (94%) patients with CNC that did not have renal cysts on imaging (p=.17). In conclusion, our data demonstrate that there is a high prevalence of renal cysts in patients with CNC with both males and females being affected equally, in contrast to the majority of previously reported population studies. They also suggest that renal cysts may develop in patients with CNC at a younger age. These results can be further validated by comparison to a cohort of healthy controls.