GRP receptor imaging of prostate cancer using [(99m)Tc]Demobesin 4 : a first-in-man study

We explored the imaging of bombesin receptors and evaluated the clinical use of [(99m)Tc]Demobesin 4 ([(99m)Tc]DB4) in prostate cancer patients.  [(99m)Tc]DB4 was prepared according to Good Manufacturing Practice. Patients with prostate cancer underwent serial planar and SPECT imaging up to 3 h after administration. Blood and urine samples were taken to assess pharmacokinetics.  [(99m)Tc]DB4 is safe and clears rapidly from the bloodstream via the kidneys resulting in low background activity. The tracer binds strongly to the gastrin-releasing peptide receptor (GRPR) in vivo as indicated by the high uptake in the pancreas seen in all patients. In patients who had undergone hormone therapy, [(99m)Tc]DB4 did not efficiently image metastatic prostate cancer. In contrast, in newly diagnosed patients local disease was visualised.  The GRPR is an unsuitable target for imaging refractory prostate cancer but may be useful in untreated disease. [(99m)Tc]DB4 is a promising radiopharmaceutical which merits further exploration in this specific group of patients

Extracellular fluid volume and glomerular filtration rate in 1,878 healthy potential renal transplant donors. Effects of age, gender, obesity and scaling.

Aim. The aim of this study was to investigate the influence of age, gender, obesity and scaling on glomerular filtration rate (GFR) and extracellular fluid volume (ECV) in healthy subjects. Methods. This is a retrospective multi-centre study of 1878 healthy prospective kidney transplant donors (819 men) from 15 centres. Age and body mass index (BMI) were not significantly different between men and women. Slope-intercept GFR was measured (using Cr-51-EDTA in 14 centres; Tc-99m-DTPA in one) and scaled to body surface area (BSA) and lean body mass (LBM), both estimated from height and weight. GFR was also expressed as the slope rate constant, with one-compartment correction (GFR/ECV). ECV was measured as the ratio, GFR to GFR/ECV. Results. ECV was age independent but GFR declined with age, at a significantly faster rate in women than men. GFR/BSA was higher in men but GFR/ECV and GFR/LBM were higher in women. Young women (65 years). There was no difference in GFR between obese (BMI > 30 kg/m2) and non-obese men. Obese women, however, had lower GFR than non-obese women and negative correlations were observed between GFR and both BMI and %fat. The decline in GFR with age was no faster in obese versus non-obese subjects. ECV/BSA was higher in men but ECV/LBM was higher in women. ECV/weight was almost gender independent, suggesting that fat-free mass in women contains more extracellular water. BSA is therefore a misleading scaling variable. Conclusion. There are several significant differences in GFR and ECV between healthy men and women

The reliability of glomerular filtration rate measured from plasma clearance: a multi-centre study of 1,878 healthy potential renal transplant donors

PURPOSE The objective of the study was to undertake a clinical audit of departmental performance in the measurement of glomerular filtration rate (GFR) using the coefficient of variation (CV) of extracellular fluid volume (ECFV) as the benchmark. ECFV is held within narrow limits in healthy subjects, narrower than GFR, and should therefore have a low CV. METHODS Fifteen departments participated in this retrospective study of healthy renal transplant donors. Data were analysed separately for men (n ranged from 28 to 115 per centre; total = 819) and women (n = 28-146; 1,059). All centres used the slope-intercept method with blood sample numbers ranging from two to five. Subjects did not fast prior to GFR measurement. GFR was scaled to body surface area (BSA) and corrected for the single compartment assumption. GFR scaled to ECFV was calculated as the terminal slope rate constant and corrected for the single compartment assumption. ECFV/BSA was calculated as the ratio of GFR/BSA to GFR/ECFV. RESULTS The departmental CVs of ECFV/BSA and GFR/BSA ranged from 8.3 to 25.8% and 12.8 to 21.9%, respectively, in men, and from 9.6 to 21.1% and 14.8 to 23.7%, respectively, in women. Both CVs correlated strongly between men and women from the same centre, suggesting department-specific systematic errors. GFR/BSA was higher in men in 14 of 15 centres, whereas GFR/ECFV was higher in women in 14 of 15 centres. Both correlated strongly between men and women, suggesting regional variation in GFR. CONCLUSION The CV of ECFV/BSA in normal subjects is a useful indicator of the technical robustness with which GFR is measured and, in this study, indicated a wide variation in departmental performance