Comparison of 99mTc-DTPA and 51Cr-EDTA for glomerular filtration rate measurement with the continuous infusion method.

BACKGROUND: In late 2018, the production of 51Chromium-labelled ethylenediamine tetra-acetic acid (51Cr-EDTA), a validated and widely used radio-isotopic tracer for measuring glomerular filtration rate, was halted. Technetium-99m-diethylenetriaminepentaacetic acid (99mTc-DTPA) has been validated for GFR measurement with a single bolus injection, a procedure not suitable in patients with extracellular compartment hyperhydration. In such cases, a bolus followed by continuous infusion of the tracer is required. The aim of this study was to evaluate whether 99mTc-DTPA with the infusion protocol can replace 51Cr-EDTA for GFR measurement. METHODS: We conducted a prospective single centre study during February and March 2019. All patients referred for GFR measurement received both radiotracers simultaneously: 51Cr-EDTA and 99mTc-DTPA bolus and continuous infusion were administered concomitantly through the same intravenous route. Over four and a half hours, plasma and urine samples were collected to calculate urinary and plasma clearance. RESULTS: Twenty-two patients were included (mean age 63.4 ± 17.5 years; 68% men). Mean urinary clearance of 51Cr-EDTA and 99mTc-DTPA was 52.4 ± 22.5 mL/min and 52.8 ± 22.6 mL/min, respectively (p = 0.47), with a mean bias of 0.39 ± 2.50 mL/min, an accuracy within 10% of 100% (95% CI 100; 100) and a Pearson correlation coefficient of 0.994. Mean plasma clearance of 51Cr-EDTA and 99mTc-DTPA was 54.8 ± 20.9 mL/min and 54.4 ± 20.9 mL/min, respectively (p = 0.61), with a mean bias of - 0.43 ± 3.89 mL/min, an accuracy within 10% of 77% (95% CI 59; 91) and a Pearson correlation coefficient of 0.983. CONCLUSIONS: Urinary and plasma clearance of 99mTc-DTPA can be used with the infusion protocol to measure GFR.

Comparison of 51Cr-EDTA and 99mTc-DTPA for glomerular filtration rate measurement.

PURPOSE: The production of 51Cr-labelled ethylenediaminetetraacetic acid (51Cr-EDTA), a validated and widely used radio-isotopic tracer for glomerular filtration rate (GFR) measurement in Europe, was recently halted by the manufacturer. Technetium-99m-diethylenetriaminepentaacetic acid (99mTc-DTPA) clearance has so far mostly been restricted to assessment of separate renal function by scintigraphy, but scarcely used and validated for GFR measurement. We compared the performances of 51Cr-EDTA and 99mTc-DTPA for GFR and extracellular fluid measurement. METHODS: In a multi-centre prospective study, 51Cr-EDTA and 99mTc-DTPA were simultaneously injected into 88 patients, and their urinary and plasma clearances, as well as their volumes of distribution, were measured during seven 30-min periods after a 90-min equilibrium time. RESULTS: Mean age was 52.2 ± 14.5 years, 59% were men. Urinary clearances of 51Cr-EDTA and 99mTc-DTPA were 64.1 ± 27.6 and 66.1 ± 28.0 mL/min, respectively, with a mean bias of 2.00 ± 2.25 mL/min, an accuracy within 10% of 95% [95% CI 91-99], and a coefficient of determination (R2) of 0.994. Plasma clearances of 51Cr-EDTA and 99mTc-DTPA were 66.1 ± 25.8 and 68.1 ± 26.6 mL/min, respectively, with a mean bias of 1.96 ± 3.32 mL/min, an accuracy within 10% of 91% [95% CI 85-97] and a R2 of 0.985. Distribution volumes were 17.3 ± 4.6 L for 51Cr-EDTA and 16.6 ± 4.6 L for 99mTc-DTPA (R2 0.930). CONCLUSION: The accuracy and precision of 99mTc-DTPA clearance, compared to 51Cr-EDTA clearance, was excellent for both urinary and plasma clearance methods, despite an approximate 2 mL/min overestimation, showing that the tracer is a reliable alternative to 51Cr-EDTA for GFR measurement.

An optimised radiolabel procedure to prepare (99m)Tc-colloidal rhenium sulphide to improve radiochemical purity.

BACKGROUND: More than 25% of 99mTc colloidal rhenium sulphide preparations have been reported to have a radiochemical purity of <95% in 11 radiopharmacies. OBJECTIVES: To identify the key parameters involved in radiochemical purity, different preparation procedures were analysed to develop an optimised preparation method. METHODS: In the first part of this study, various data such as the Nanocis kit batch number, the eluate volume, the time between the two final elutions, the temperature and duration of heating were collected and analysed to determine the critical parameters that significantly decrease radiochemical purity. In the second part, a new procedure was applied and then the same parameters and radiochemical purity values were collected and compared with the results before the new procedure. RESULTS: Among 184 preparations, 137 (75%) had a radiochemical purity exceeding 95%, 25 (13.6%) were between 90 and 95% pure and 22 (12%) were below 90%. Significantly higher radiochemical purity was observed after the implementation of the new preparation procedure (89.5% of 374 preparations had radiochemical purities of > 95%). This new procedure consists in lowering the 99mTc eluate volume and time of heating. CONCLUSIONS: The implementation of a new method for the preparation of (99m)Tc colloidal rhenium sulphide based on a comparison of practices in various radiopharmacies resulted in: i) a determination of the critical points of this preparation, ii) an optimised labelling technique to harmonise different practices, and iii) a significant improvement in the preparations radiochemical purity and the quality of the lymphoscintigraphy in the location of sentinel node.

Metastatic renal cell carcinoma: relationship between initial metastasis hypoxia, change after 1 month's sunitinib, and therapeutic response: an 18F-fluoromisonidazole PET/CT study.

UNLABELLED: The aims of this cohort study were to evaluate initial tumor hypoxia in metastatic renal cell carcinoma (mRCC) and its changes after sunitinib treatment, using (18)F-fluoromisonidazole PET/CT, and investigate the possible prognostic value of initial tumor hypoxia or its changes under sunitinib therapy. METHODS: Antiangiogenic-naive patients with mRCC were prospectively enrolled in this cohort study. Before initiation of sunitinib, CT defined up to 10 targets that were assessed at 1 and 6 mo according to the response evaluation criteria in solid tumors (RECIST). Pretreatment target uptake of (18)F-fluoromisonidazole was compared with uptake at 1 mo. Targets were considered hypoxic when their maximal standard uptake value was above mean blood value + 2 SDs. Hypoxic volumes were also computed. Relationships between initial hypoxia status, initial degree of hypoxia, its change at 1 mo, and overall or progression-free survival (OS and PFS, respectively) were assessed by survival analysis. RESULTS: Fifty-three patients were included. Median follow-up was 16.8 mo. (18)F-fluoromisonidazole uptake significantly decreased in initially hypoxic target metastases but did not change in others (-22%, P < 10(-4), vs. +1.5%, P = 0.77; P = 10(-3) between groups). Seventy-five percent of patients with hypoxic metastases were free of progressive disease at 4.8 mo (95% confidence interval, 2.99-11.83), compared with 11.3 mo (95% confidence interval, 3.08-36.9) for other patients (P = 0.02), whereas OS was not significantly different. Changes in tumor hypoxia were not related to PFS or OS. CONCLUSION: Sunitinib reduced hypoxia in initially hypoxic RECIST target metastases but did not induce significant hypoxia in nonhypoxic RECIST target metastases. Patients with initially hypoxic targets have shorter PFS than others.