Abstract
PurposeProstate-specific membrane antigen (PSMA)-targeted PET is increasingly used for staging prostate cancer (PCa) with high accuracy to detect significant PCa (sigPCa). [68 Ga]PSMA-11 PET/MRI-guided biopsy showed promising results but also persisting limitation of sampling error, due to impaired image fusion. We aimed to assess the possibility of intraoperative quantification of [18F]PSMA-1007 PET/CT uptake in core biopsies as an instant confirmation for accurate lesion sampling.MethodsIn this IRB-approved, prospective, proof-of-concept study, we included five consecutive patients with suspected PCa. All underwent [18F]PSMA-1007 PET/CT scans followed by immediate PET/CT-guided and saturation template biopsy (3.1 ± 0.3 h after PET). The activity in biopsy cores was measured as counts per minute (cpm) in a gamma spectrometer. Pearson’s test was used to correlate counts with histopathology (WHO/ISUP), tumor length, and membranous PSMA expression on immunohistochemistry (IHC).ResultsIn 43 of 113 needles, PCa was present. The mean cpm was overall significantly higher in needles with PCa (263 ± 396 cpm) compared to needles without PCa (73 ± 44 cpm, p < 0.001). In one patient with moderate PSMA uptake (SUVmax 8.7), 13 out of 24 needles had increased counts (100–200 cpm) but only signs of inflammation and PSMA expression in benign glands on IHC. Excluding this case, ROC analysis resulted in an AUC of 0.81, with an optimal cut-off to confirm PCa at 75 cpm (sens/spec of 65.1%/87%). In all 4 patients with PCa, the first or second PSMA PET-guided needle was positive for sigPCa with high counts (156–2079 cpm).Conclusions[18F]PSMA-1007 uptake in PCa can be used to confirm accurate lesion sampling of the dominant tumor intraoperatively. This technique could improve confidence in imaging-based biopsy guidance and reduce the need for saturation biopsy.Trial registration numberNCT03187990, 15/06/2017.
Highlights
Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is a well-established technique for the assessment of prostate cancer (PCa) biochemical recurrence (BCR) [1] with a significant impact on patient management due to high sensitivity and specificity [2]
Most of the studies are retrospective and composed of intermediate to high-risk PCa patients [3,4,5,6]. These tumors are more likely to overexpress PSMA; a potential bias and overestimated accuracy is possible. [68 Ga]PSMA-11 PET may represent a useful tool to improve the accuracy of imaging-guided biopsy in PCa [7], even if data are still limited, and [68 Ga]PSMA-11 PETbiopsy guidance is nowadays recommended only in patients with previous negative biopsy [8]
The first tracer with broad application was [68 Ga]PSMA-11; with a high urinary excretion, this tracer sometimes limited the detection of local recurrence
Summary
Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) is a well-established technique for the assessment of prostate cancer (PCa) biochemical recurrence (BCR) [1] with a significant impact on patient management due to high sensitivity and specificity [2]. Most of the studies are retrospective and composed of intermediate to high-risk PCa patients [3,4,5,6] These tumors are more likely to overexpress PSMA; a potential bias and overestimated accuracy is possible. When using [68 Ga]PSMA-11 PET/magnetic resonance imaging (MRI), a high correlation between sigPCa on saturation biopsy has been reported with a sensitivity of 96%; [68 Ga]PSMA-11 PET/MRItargeted needles only reached a suboptimal sensitivity of 65% [13]. This is probably due to the difficulties in imageguided biopsy with the inherent risk to miss the target. Due to the high accumulation of [68 Ga]/[18F] PSMA in sigPCa, we assumed that an intraoperative confirmation of high photon counts in the biopsy core could be used as a prompt confirmation for needle allocation within the targeted lesion
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