Estimation of split renal function on PET using the SSTR-targeting radioligands [¹⁸F]SiTATE, [⁶⁸Ga]Ga-DOTA-TATE and [⁶⁸Ga]Ga-DOTA-TOC in a theranostic setting.

Abstract

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 [¹⁷⁷Lu]Lu-DOTA-TATE therapy. In this retrospective study, 85 NEN patients treated with [¹⁷⁷Lu]Lu-DOTA-TATE between 2013 and 2023 were included. All underwent SSTR-PET/CT using [¹⁸F]SiTATE, [⁶⁸Ga]Ga-DOTA-TATE, or [⁶⁸Ga]Ga-DOTA-TOC plus serum kidney function tests and [^99mTc]Tc-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. Renal uptake on SSTR-PET/CT moderately correlated with split renal function assessed by [^99mTc]Tc-MAG3 across all tracers, particularly using SUV_mean ([¹⁸F]SiTATE (r = 0.462; p = 0.010); [⁶⁸Ga]Ga-DOTA-TATE (r = 0.515; p = 0.004); [⁶⁸Ga]Ga-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 ([¹⁸F]SiTATE; r = 0.585; p = 0.076; [⁶⁸Ga]Ga-DOTA-TATE; r = 0.649; p = 0.049). A strong negative correlation between TER and absorbed dose was seen only for [¹⁸F]SiTATE (r = - 0.768; p = 0.010). 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.