Clinicopathological predictors of positive 68 Ga-PSMA-11 PET/CT in PSA-only recurrence of localized prostate cancer following definitive therapy

Abstract

Objective

To demonstrate the effect of clinicopathological factors on ⁶⁸Ga-PSMA-11 PET/CT positivity at the time of biochemical recurrence (BCR) of localized prostate cancer (PCa) following definitive therapy.

Methods

We retrospectively reviewed our institutional database for PCa patients who had BCR and subsequently underwent ⁶⁸Ga-PSMA-11 PET/CT between April 2014 and February 2018. A total of 51 patients who were metastasis-free before PSMA imaging and previously treated with definitive therapy (radical prostatectomy or external beam radiotherapy) for localized disease (pT1c—T3b pN0-1 cM0) were included.

Results

37 out of 51 patients (72.5%) had positive ⁶⁸Ga-PSMA-11 PET/CT scans. Age at diagnosis, Gleason score (GS), D'Amico risk status of PCa, initial PSA level before treatment and PSA doubling time were not associated with PSMA positivity. Pre-scan PSA levels of > 0.2 ng/ml and PSA velocity of ≥ 1 ng/ml/year were significantly associated with increased PSMA positivity, whereas history of androgen deprivation therapy showed a trend towards significance. The optimal cutoffs for distinguishing between positive and negative scans were ≥ 0.71 ng/ml for pre-scan PSA and ≥ 1.22 ng/ml/yr for PSA velocity. In multivariable analysis, log pre-scan PSA and pre-scan PSA level > 0.2 ng/ml remained significant predictors for PSMA positivity, whereas the association of PSA velocity and of ADT was lost.

Conclusions

In BCR of localized PCa following definitive therapy, pre-scan PSA was strongly associated with positive ⁶⁸Ga-PSMA-11 scan, even at PSA levels ranging from 0.2 to 1.0 ng/ml. Therefore, clinical and pathological predictors of positive ⁶⁸Ga-PSMA-11 PET/CT in PSA-only recurrence of localized prostate cancer need to be further elucidated.

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