This large prospective intraindividual comparison of [ 18 F]PSMA-1007 PET/CT vs [ 68 Ga]Ga-PSMA-11 PET/CT has demonstrated overall high concordance (92%) for TNM stage in the context of prostate cancer primary staging, biochemical recurrence and evaluation of patients with metastatic disease. Reduced [ 18 F]PSMA-1007 urinary radiotracer excretion improves characterisation of disease adjacent the bladder (prostate or prostate bed following de nitive treatment, including local invasion) and ureters (peri-ureteric nodes) compared to [ 68 Ga]Ga-PSMA-11. [ 18 F]PSMA-1007 demonstrates signi cantly higher uptake within involved nodes and bone metastases, and physiologic tissues including liver, spleen, neural ganglia, bone marrow and benign nodes. Inexperienced reporters of [ 18 F]PSMA-1007 PET should understand that hepatic uptake may obscure metastases within the liver or adjacent adrenal gland, and that [ 18 F]PSMA-1007 is associated with more equivocal bone lesions. Both tracers are acceptable for imaging of prostate cancer, with factors in uencing choice including availability (local generator production of [ 68 Ga]Ga-PSMA-11 vs external cyclotron supply [ 18 F]PSMA-1007), preference for improved characterisation of disease in the prostate and pelvic nodes (favouring [ 18 F]PSMA-1007) versus likelihood of visceral metastasis (favouring [ 68 Ga]Ga-PSMA-11) and the experience of reporting specialists to exclude benign patterns of uptake, particularly neural ganglia and equivocal bone lesions.
We present a case of Ga-PSMA PET/CT imaging of PSMA expression in neurofibromas in a patient with neurofibromatosis type 1 (or von Recklinghausen disease). PSMA uptake has previously been demonstrated in schwannomas both with PET and histological staining. The presented images confirm that PSMA expression in cutaneous neurofibromas can be well imaged with PET, with uptake mostly at relatively low levels. Interestingly, some lesions demonstrated significantly higher PSMA expression, although the clinical significance of these differences remains to be determined. The images raise the possibility of a potential role for Ga-PSMA PET/CT in neurofibromatosis type 1 monitoring.
Introduction[18F]PSMA-1007 has potential advantages over [68Ga]Ga-PSMA-11, although limited prospective data evaluating diagnostic performance exist. The aims of this study are to describe the concordance of [18FPSMA-1007 and [68Ga]Ga-PSMA-11 for TNM with American Joint Committee on Cancer (AJCC) prognostic stage, and assess differences in tracer uptake.MethodsFifty men (mean age 71.8) were imaged with [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 < 4 weeks apart. Images were independently reported according to TNM by two experienced nuclear medicine specialists blinded to the other scan and prior imaging. Discordant results were resolved by a third independent nuclear medicine specialist. Quantitative analysis of lesion uptake and physiologic tissue for each tracer was performed by one experienced reader.ResultsScan indications were initial staging (n = 12), biochemical recurrence (n = 27) and metastatic disease evaluation (n = 11). Most patients had ISUP grade group 3 or higher. Median PSA value was 2.7 ng/ml (IQR 0.7–12.0) and a minority of patients (28%) were currently treated with androgen deprivation therapy. [18F]PSMA-1007 uptake was significantly higher than [68Ga]Ga-PSMA-11 in local recurrence, nodal and distant metastases, and most physiologic sites except for urinary bladder which was significantly lower. [18F]PSMA-1007 upstaged local prostate staging in 5/17 patients, local recurrence in 3/33 patients, regional nodal disease in 3/50 patients and 1 distant metastasis (bladder). [68Ga]Ga-PSMA-11 upstaged regional nodal disease in 1/50 patients and distant metastasis in one patient (right adrenal). Overall AJCC prognostic stage was concordant in 46/50 (92%) patients, with two patients upstaged for both [18F]PSMA-1007 and [68Ga]Ga-PSMA-11. [18F]PSMA-1007 had more equivocal results (one regional node; six equivocal bone lesions, one of which was subsequently confirmed metastatic) than [68Ga]Ga-PSMA-11 (one equivocal local recurrence).ConclusionOverall AJCC prognostic stage was similar (92%) between [18F]PSMA-1007 and [68Ga]Ga-PSMA-11. [18F]PSMA-1007 demonstrates higher uptake within involved nodes and distant metastases, and most physiologic sites except urinary bladder which aided [18F]PSMA-1007 local staging of the prostate primary / local recurrence and regional nodal disease adjacent ureters. However [18F]PSMA-1007 liver uptake obscured a solitary right adrenal metastasis, and more equivocal bone lesions were identified.
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