Molecular imaging for the detection of kidney fibrosis in patients with varying chronic kidney disease (CKD) stages

Ziel/Aim Kidney fibrosis leads to a progressive reduction in kidney function resulting finally in kidney failure. Diagnostic tools to detect kidney fibrosis are all invasive in nature with the need of kidney biopsies with subsequent histological validation. In this retrospective study the diagnostic value of three different radiotracers for the non-invasive prediction of kidney fibrosis is analyzed, taking into account the current Chronic Kidney Disease (CKD) stage and the intra-renal parenchymal radiotracer uptake of the patient.

Methodik/Methods Renal uptake of the three PET-tracers [⁶⁸Ga]Ga-FAPI, [⁶⁸Ga]Ga-PSMA and [⁶⁸Ga]Ga-DOTATOC was quantified using SUV_max and SUV_mean at separate regions of the renal parenchyma. Background activity was measured in lung, myocardium and gluteal muscle whereas blood pool activity was measured in the abdominal aorta. In total 81 PET/CT scans were retrospectively analyzed (FAPI n = 20, DOTATOC n = 27, PSMA n = 34). The patients were classified in either one of the four stages of Chronic Kidney Disease (CKD) and the SUV_max and SUV_mean values were compared using univariate analysis test.

Ergebnisse/Results Statistical analysis revealed a positive correlation between CKD stage [⁶⁸Ga]Ga-FAPI uptake for both SUV_max and SUV_mean values. This correlation was seen for all locations of the renal parenchyma. Regarding the background and the blood pool uptake, only the myocard showed a significant correlation. The PET-radiotracers [⁶⁸Ga]Ga-DOTATOC and [⁶⁸Ga]Ga-PSMA-L did not show a positive correlation between CKD stage and intra-renal parenchymal radiotracer uptake, as well as for the background and blood pool uptake.

Schlussfolgerungen/Conclusions There is a significant positive correlation between renal parenchymal [⁶⁸Ga]GaFAPI uptake and CKD stage of the patient, which was not the case for [⁶⁸Ga]Ga-DOTATOC and [⁶⁸Ga]Ga-PSMA-L. This suggests a specific binding of FAPI rather than a potential unspecific retention in the renal parenchym. Therefore, the use of [⁶⁸Ga]Ga-FAPI in preclinical kidney fibrosis models is a promising step in the further evaluation of this PET-radiotracer for a potential implementation as a diagnostic tool for kidney fibrosis.