68Ga-HBEDD PSMA-11 PET/CT staging prior to radical prostatectomy in prostate cancer patients: Diagnostic and predictive value for the biochemical response to surgery

Objective: To determine the predictive and diagnostic value of 68Ga-HBEDD PSMA-11 positron emission tomography (PET)/CT (prostate-specific membrane antigen, PSMA) for surgical response in males with prostate cancer prior to radical prostatectomy. Methods: We analysed results of 142 males with staging PSMA prior to radical prostatectomy (RP). Data collected included PSMA PET/CT, bone scan (30/142), mpMRI (112/142), and pathological T stage (pT) stage, Gleason score, surgical margins and lymph node status at RP. Prostate-specific antigen (PSA) was documented at staging scan, and following surgery (median 45 days (interquartile range 38-59). A PSA of < 0.03 ng ml-1 was classified as surgical response (SR). Logistic regression was performed for association of pre-operative clinical variables and SR. Results: 97.9% (139/142) of males had positive intraprostatic findings on PSMA. 14.1 % (20/142) of males had further sites of extra prostatic disease identified on PSMA PET. In males with disease confined to the prostate, 82.9 % (92/111) achieved an SR, compared to 28.6 % (4/14) in males with extraprostatic disease identified (lymph node positive and distant metastatic disease) (p < 0.001). On binary logistic regression PSMA had a superior predictive value for SR than Gleason score, PSA (at time of imaging) or pT stage. MRI was less sensitive and more specific for SVI, and less sensitive for nodal involvement. Conclusion: Extraprostatic disease identified on staging pre-operative PSMA PET is independently predictive of a poor surgical response to RP, and may indicate a need for a multimodality approach to treatment. Advances in knowledge: This is one of the first studies to correlate the PSMA PET's staging capacity to prostate cancer patient's outcomes to radical prostatectomy and indicates it's potential in predicting which patients will benefit from radical prostatectomy.