A Comparative Study of 18F-FAPI-42 and 18F-FDG PET/CT for Evaluating Acute Kidney Injury in Cancer Patients

Abstract

Purpose: Compare the value of imaging using positron ¹⁸F-labeled fibroblast activation protein inhibitor-42 (¹⁸F-FAPI-42) and ¹⁸F-labeled deoxyglucose (¹⁸F-FDG) for assessment of AKI.

Procedures: This study analyzed cancer patients who received ¹⁸F-FAPI-42 and ¹⁸F-FDG PET/CT imaging. Eight patients had AKI with bilateral ureteral obstruction (BUO), eight had BUO (CKD1-2) with no acute kidney disease (AKD), and eight had no ureteral obstruction (UO) with normal renal function. The average standardized uptake value (SUV_ave) of the renal parenchyma (RP-SUV_ave), the blood pool SUV_ave (B- SUV_ave), SUV_ave in the highest region of the renal collective system (RCS-SUV_ave), and the highest serum creatinine level (top SCr) were recorded.

Results: The ¹⁸F-FAPI-42 and ¹⁸F-FDG results showed that radiotracer of renal parenchyma was more concentrated in the AKI group than in the other two groups, whereas the RP-SUV_ave from ¹⁸F-FAPI-42 was higher than that from ¹⁸F-FDG in the AKI group (all P < 0.05). ¹⁸F-FAPI-42 imaging in the AKI group showed uptake by the renal parenchyma with a diffuse increase, but very little radiotracer in the renal collecting system, similar to a "super kidney scan." The renal parenchyma also had an increase of SUV_ave, with accumulation of radiotracer in the renal collecting system. AKI was more severe when a patient had a "super kidney scan" in both kidneys (P < 0.05). The B-SUV_ave level was higher in the AKI group than in the other two groups in ¹⁸F-FAPI-42 (both P < 0.05).

Conclusions: ¹⁸F-FAPI-42 imaging had higher RP-SUV_ave than ¹⁸F-FDG imaging in cancer patients who had BUO with AKI. An increased renal parenchyma uptake in both kidneys and low radiotracer distribution in the collecting system suggest more severe AKI.

Keywords: AKI: acute kidney injury; FAPI: fibroblast activation protein inhibitor; FDG: fluorodeoxyglucose; PET/CT; UO: ureteral obstruction.