Early Detection of Biochemical Recurrence in Prostate Cancer Patients with PSA Levels ≤0.5 ng/mL; Comparison Study between [¹⁸F]PSMA-1007 and [⁶⁸Ga]Ga-PSMA-11 PET/CT.

Abstract

Purpose: This study compared the correct detection rates (CDR) of [¹⁸F]PSMA-1007 and [⁶⁸Ga]Ga-PSMA-11 positron emission tomography/computed tomography (PET/CT) in patients with prostate-specific antigen (PSA) ≤0.5 ng/mL after radical prostatectomy.

Materials and methods: This retrospective study included 88 patients who underwent [¹⁸F]PSMA-1007 (n=41) or [⁶⁸Ga]Ga-PSMA-11 PET/CT (n=47) for PSA ≤0.5 ng/mL after radical prostatectomy. Patients were stratified into ultra-low biochemical recurrence (u-BCR, <0.2 ng/mL) and early BCR (e-BCR, 0.2-0.5 ng/mL) groups. CDRs, defined as the proportion of patients with true positive findings for each imaging modality, and positive predictive values (PPVs) were compared between radiotracers.

Results: The overall CDR of [¹⁸F]PSMA-1007 was significantly higher than [⁶⁸Ga]Ga-PSMA-11 (70.7% vs. 23.4%, p<0.001) in both u-BCR (60.0% [9/15] vs. 19.0% [4/21], p=0.017) and e-BCR groups (76.9% [20/26] vs. 26.9% [7/26], p<0.001). Local recurrence was more frequently detected with [¹⁸F]PSMA-1007, particularly in the e-BCR group (46.2% vs. 3.8%, p<0.001), while lymph node (LN) and distant metastases detection was comparable. In the u-BCR group, the recurrence sites identified by [¹⁸F]PSMA-1007 included local (n=3), LN (n=3), bone (n=2), and local plus LN (n=1), whereas [⁶⁸Ga]Ga-PSMA-11 identified local (n=1), LN (n=1), bone (n=1), and lung (n=1). In [¹⁸F]PSMA-1007, CDR was higher in high/very high-risk than in low/intermediate-risk patients in the u-BCR group (p=0.011). No such difference was observed with [⁶⁸Ga]Ga-PSMA-11. PPVs did not differ significantly between radiotracers (p=0.333).

Conclusions: [¹⁸F]PSMA-1007 PET/CT showed higher CDR than [⁶⁸Ga]Ga-PSMA-11 PET/CT in patients at PSA ≤0.5 ng/mL after radical prostatectomy. Given the high detection performance, these findings support consideration of [¹⁸F]PSMA-1007 PET/CT for detection at PSA ≤0.5 ng/mL, particularly for prostate bed assessment in high/very high-risk patients.