Uptake patterns of PSMA PET in brain tumors: comparative analysis of [68Ga]Ga-PSMA-11 or [18F]PSMA-1007 PET with [18F]FET PET and contrast-enhanced MRI

Ziel/Aim: Radioligand therapies are under investigation in various cancers, and [¹⁷⁷Lu]Lu-PSMA-617 is approved in prostate cancer. Expression of PSMA has been shown in brain tumors, but data on uptake patterns of PSMA PET in relation to contrast-enhanced MRI and amino acid PET are scarce.

Methodik/Methods: Patients with intracranial malignancies who underwent [⁶⁸Ga]Ga-PSMA-11 or [¹⁸F]PSMA-1007 PET+/- [¹⁸F]FET-PET were included. PSMA PET-positive volume (PSMA+) was segmented using a SUV threshold>blood pool activity, while FET PET-positive volume (FET+) was segmented as SUV>1.6 x SUV_mean of background (contralateral white/grey matter). Contrast-enhancing volume in MRI (CE+) was segmented manually, and Dice coefficients for similarity of volumes were calculated.

Ergebnisse/Results: 15 patients were included (9 [60.0%] glioblastoma, 4 [26.7%] IDH-mutant glioma, 2 [13.3%] prostate cancer brain metastases [BM]). 18 PSMA PET and 13 FET PET studies have been performed, and 28 lesions have been evaluated. In PSMA PET, SUV_max was highest in BM (median 2.5, range: 2.2 – 2.8), followed by glioblastoma (1.8 [1.0 – 5.2]) and IDH-mut glioma (1.0 [0.1 – 2.3]); p=0.026), as was TBR_max (BM: 3.1 [2.2 – 4.0]; glioblastoma: 3.0 [1.2 – 12.0]; IDH-mut glioma: 0.8 [0.1 – 2.9]; p=0.002). Uptake intensity (SUV_max; TBR_max) was higher in FET PET than PSMA PET (p<0.001). FET+volumes exceeded PSMA+volumes (median: 1.22 ml [0 – 77.2] vs. 4.72 ml [0 – 115.0]; p<0.001), while no difference was found between PSMA+and CE+volumes (median: 1.73 ml [0 – 36.4]; p=0.65). Only partial volume overlaps were observed, as median Dice coefficients in glioblastoma were 0.5 [0.126 – 0.791] for PSMA+/FET+and 0.453 [0.156 – 0.811] for PSMA+/CE+volumes, while they were numerically lower in IDH-mutant gliomas (PSMA+/FET+: 0.405 [0.030 – 0.611], p=0.432; PSMA+/CE+: 0.175 [0 – 0.522]; p=0.056). In median, PSMA+/FET+overlaps account for only 36.5% of FET+volumes in glioblastoma (range: 6.7% – 66.2%), whereas PSMA+/CE+overlaps constitute 62.8% [17.8% – 94.1%] of CE+volume.

Schlussfolgerungen/Conclusions: Particularly in glioblastoma, PSMA uptake is mainly found in CE+areas with disrupted BBB. As the extent of metabolically active tumor tissue delineated by FET PET overall exceeds PSMA+areas, methods to open the BBB such as focused ultrasound should be evaluated for theranostic applications.

Publikationsverlauf

Artikel online veröffentlicht:
12. März 2025