Abstract
[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 the American Joint Committee on Cancer (AJCC) prognostic stage and assess differences in tracer uptake. Fifty men (mean age 71.8) were imaged with [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 < 4weeks 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. Scan 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 2.7ng/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 (including bone) 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). Overall 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. Trial registration The study was registered with Australia New Zealand Clinical Trials Registry (ACTRN12618000665235) on 24 April 2018.
Highlights
Prostate cancer is responsible for an estimated 366 000 deaths annually worldwide and is the most commonly diagnosed male cancer in Australia[1]
From May to December 2018, 50 men were recruited according to the following eligibility criteria: (a) aged 18 years or older, (b) provided informed consent and able to comply with the study procedures, and (c) fit the criteria for one of the following scan indication categories: primary staging, biochemical recurrence or restaging of distant metastatic disease
Metastatic disease was defined as known metastatic prostate cancer diagnosed by at least one of [68Ga]Ga-Prostate specific membrane antigen (PSMA)-11, whole body bone scan, CT or MRI imaging or histopathologic confirmation of prostate cancer metastasis
Summary
Prostate cancer is responsible for an estimated 366 000 deaths annually worldwide and is the most commonly diagnosed male cancer in Australia[1]. The first of these, [68Ga]GaPSMA-11 rapidly became commonly used and suggested as the new standard of care for staging[4], restaging at biochemical recurrence[5] and theranostic approach to prostate malignancy[6] given its superior sensitivity and specificity, interobserver reliability[7] and correlation with [177Lu]Lu-PSMA-617 tumour dosimetry and treatment outcomes[8]. Urinary excretion of [68Ga]Ga-PSMA-11 radiotracer may limit identification of small volume disease adjacent to the ureters, bladder and prostatic urethra[9] requiring use of contrast or diuretics and their associated side effects in some centres. Intense urinary uptake in the bladder and kidneys may lead to a flair/halo artefact, limiting the detection of disease in adjacent pelvic tissues[10]. Incorrect 68Ga dose calibration may impact upon quantitative accuracy[11]
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