Background
Most scientific data on 68Ga‐PSMA PET/CT is for the evaluation of recurrent disease after primary treatment. To our knowledge this study is the largest series of primary prostate cancer staging with 68Ga‐PSMA PET/CT.
Objective
To determine the number of men with 68Ga‐PSMA PET/CT avid metastasis at diagnosis.
Design, Setting and Participants
A retrospective review conducted on 1253 consecutive men referred by urologists or radiation oncologists to our tertiary referral centre for 68Ga‐PSMA PET/CT scan for staging at the initial diagnosis of prostate cancer between July 2014 and June 2018.
Outcome Measurements and Statistical Analysis
Primary outcome measure was to determine the risk of metastasis based on 68Ga‐PSMA PET/CT. Patients were risk stratified based on biopsy histological ISUP grade, PSA and staging with pre‐biopsy multiparametric MRI scan to determine. Univariate and multivariate logistic regression was used to analyse results.
Results and Limitations
The median PSA was 6.5ng/mL and median ISUP grade 3, with high risk disease in 49.7%. The prostate primary was PSMA‐avid in 91.7% of men.
Metastatic disease was identified in 12.1% of men, including 8.2% with PSA <10ng/mL and 43% with PSA >20ng/mL. Metastases were identified in 6.4% with ISUP 2‐3 and 21% with ISUP 4‐5. Pre‐biopsy mpMRI identified metastasis in 8.1% of T2 disease, increasing to 42.4% of T3b.
Lymph node metastases were suspected in 107 men, with 47.7% outside the boundaries of an extended pelvic lymph node dissection. Skeletal metastases were identified in 4.7%. In men with intermediate risk prostate cancer metastases were identified in 5.2%, compared to 19.9% with high risk disease.
Conclusions
These results support the use of 68Ga‐PSMA PET/CT for primary staging of prostate cancer. Increasing PSA level, ISUP grade and radiological staging with mpMRI were all statistically significant prognostic factors for metastasis on both univariate and multivariate analysis.