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. 2024 Mar 8;14(6):578.
doi: 10.3390/diagnostics14060578.

A Comparison of 68Ga-PSMA PET/CT-Based Split Renal Function with 99mTc-MAG3 Renography in Patients with Metastatic Castration-Resistant Prostate Carcinoma Treated with 177Lu-PSMA

Lerato Gabela  1   2 , Thokozani Mkhize  1   2 , Bawinile Hadebe  1   2 , Lerwine Harry  1   2 , Thembelihle Nxasana  1   2 , Nontobeko Ndlovu  1   2 , Venesen Pillay  1   2 , Sphelele Masikane  1   2 , Maryam Patel  1   2 , Nozipho Elizabeth Nyakale  3 , Mariza Vorster  1   2
Affiliations

A Comparison of 68Ga-PSMA PET/CT-Based Split Renal Function with 99mTc-MAG3 Renography in Patients with Metastatic Castration-Resistant Prostate Carcinoma Treated with 177Lu-PSMA

Lerato Gabela et al. Diagnostics (Basel). .

Abstract

Background: Physiological PSMA expression in the cells of the proximal renal tubules and consecutive radiopharmaceutical binding and retention could potentially lead to radioligand-therapy-induced nephrotoxicity. Thus, patients with metastatic castration-resistant prostate cancer undergo 99mTc-Mercaptoacetyltriglycine (MAG3) renal scintigraphy to assess kidney function and to exclude renal obstruction as part of their workup for PSMA-targeted radioligand therapy (RLT). 99mTc-MAG-3 renal scintigraphy often requires an additional visit to the nuclear medicine department and patients spend 30-90 min in the department, which is inconvenient and takes up camera time. In addition, the patients are subjected to a baseline 68Ga-PSMA PET/CT to assess for PSMA-positive disease prior to targeted radioligand therapy. The aim of this retrospective cross-sectional study was to compare 99mTc-MAG-3-based split renal function (SRF) with 68Ga-PSMA-derived SRF.

Methods: This retrospective cross-sectional study included 28 patients with histologically proven metastatic castration-resistant prostate cancer (mCRPC) who received 177Lu-PSMA617. A comparison between the split renal function using 68Ga-PSMA PET/CT and the 99mTc-MAG-3-derived split renal function was carried out in 56 kidneys (n = 56). The SRF on 68Ga-PSMA was calculated using the volume and the average standard uptake value (SUVmean) within each VOI calculated as previously described by Roser et al.: SRF = (VOLUMEright) ∗ SUVmeanright/(VOLUMEright ∗ SUVmeanright + VOLUMEleft ∗ SUVmeanleft). Paired tests and correlation coefficients were used to compare 68Ga-PSMA and 99mTc-MAG-3. A visual comparison of kidney morphology on both studies was also performed.

Results: The median SRF of the right kidney was 49.9% (range: 3-91%) using 68Ga-PSMA PET/CT and 50.5% (range: 0-94%) with 99mTc-MAG3 scintigraphy. Notably, there was a strong correlation between SRF measurements obtained from PSMA and 99mTcMAG3, with a Pearson correlation coefficient of 0.957 (p < 0.001). Both 99mTc-MAG3 and 68Ga-PSMA PET/CT studies identified morphological renal abnormalities; there were nine hydronephrotic kidneys, four shrunken kidneys and one obstructed kidney, and there was a strong positive correlation between 68Ga-PSMA kidney morphology and 99mTcMAG3 renal scintigraphy kidney morphology, with a correlation coefficient of 0.93.

Conclusions: PSMA-derived split function demonstrated a high correlation with renal function assessed on diuretic 99mTc-MAG3 renograms. PET-derived split renal function may, therefore, be considered an alternative to diuretic renogram-based split function. Furthermore, both 99mTc-MAG3 and 68Ga-PSMA PET/CT studies identified morphological renal abnormalities such as hydronephrosis, shrunken and obstructed kidneys. This correlation underscores the potential utility of 68Ga-PSMA imaging as a valuable tool for assessing kidney morphology as an alternative to renogram split function in clinical practice.

Keywords: 68Ga PSMA-11; 99mTc-MAG3; PET/CT; kidney; renal function.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
The distribution of creatinine, urea, PSA and Gleason score in the study population.
Figure 2
Figure 2
The distribution of eGFR in the study population.
Figure 3
Figure 3
A positive correlation between the 68Ga-PSMA- and 99mTc-MAG-3-derived SRF in the right kidney.
Figure 4
Figure 4
A positive correlation between the 68Ga PSMA- and 99mTc-MAG-3-derived SRF in the left kidney.
Figure 5
Figure 5
Boxplot showing the recorded differences between the renogram and the PET data. The SRF is centrally located with a few outliers.
Figure 6
Figure 6
Histogram comparison for 68Ga-PSMA kidney morphology and 99mTc-MAG3 kidney morphology, with a correlation coefficient of approximately 0.93.
Figure 7
Figure 7
A case of a patient with normal renal function and equal SRF. (A) 68Ga PSMA PET; (B) 99mTc-MAG3.
Figure 8
Figure 8
99mTc-MAG3 renogram (A) showing an area of photopenia in a non-functioning right kidney, which is confirmed on the 68Ga-PSMA PET/CT images; (B) showing a right kidney with decreased tracer uptake and a dilated collecting system.
Figure 9
Figure 9
99mTc-MAG3 renogram images (A) showing left kidney obstruction. 68Ga PSMA PET/CT images (B) showing multiple kidney cysts bilaterally with decreased tracer uptake and a stasis of radiotracer in a dilated collecting system.
Figure 10
Figure 10
68Ga-PSMA PET/CT images (A) showing a shrunken left kidney with decreased tracer uptake. 99mTc-MAG3 renogram (B) showing an area of photopenia in a non-functioning left kidney.
See this image and copyright information in PMC

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