Estimation of split renal function on PET using the SSTR-targeting radioligands 18FSiTATE, 68GaGa-DOTA-TATE and 68GaGa-DOTA-TOC in a theranostic setting

Abstract Purpose SSTR-PET is routinely used to select patients with neuroendocrine neoplasms (NEN) for peptide receptor radionuclide therapy (PRRT). As the kidneys are organs at risk, this study evaluated whether renal uptake on pre-therapeutic SSTR-PET/CT reflects split or global renal function and correlates with renal absorbed dose during 177 LuLu-DOTA-TATE therapy. Methods In this retrospective study, 85 NEN patients treated with 177 LuLu-DOTA-TATE between 2013 and 2023 were included. All underwent SSTR-PET/CT using 18 FSiTATE, 68 GaGa-DOTA-TATE, or 68 GaGa-DOTA-TOC plus serum kidney function tests and 99m TcTc-MAG3 scintigraphy. Renal PET uptake was compared with serum and scintigraphic kidney parameters. In 30 patients, renal absorbed dose was estimated using post-treatment SPECT/CT. Results Renal uptake on SSTR-PET/CT moderately correlated with split renal function assessed by 99m TcTc-MAG3 across all tracers, particularly using SUV mean ( 18 FSiTATE ( r = 0.462; p = 0.010); 68 GaGa-DOTA-TATE ( r = 0.515; p = 0.004); 68 GaGa-DOTA-TOC ( r = 0.546; p = 0.004)). No relevant correlation was observed between total renal PET uptake and tubular extraction rate, eGFR, or serum creatinine. Renal PET uptake showed moderate correlations with mean absorbed doses in selected tracer cohorts ( 18 FSiTATE; r = 0.585; p = 0.076; 68 GaGa-DOTA-TATE; r = 0.649; p = 0.049). A strong negative correlation between TER and absorbed dose was seen only for 18 FSiTATE ( r = − 0.768; p = 0.010). Conclusion SSTR-PET/CT showed moderate potential to estimate pre-therapeutic split renal function and renal absorbed dose. However, global renal function could not be reliably estimated using PET/CT. Larger studies are warranted to validate PET/CT-based kidney assessment for individualized PRRT planning.