⁶⁸Ga-PSMA-11 PET/CT detects prostate cancer at early biochemical recurrence with superior detection rate and reader agreement when compared to ¹⁸F-Fluciclovine PET/CT in a prospective head-to-head comparative phase 3 study

Purpose: This is a prospective single-center, single-arm, head-to-head phase 3 comparative study of paired ¹⁸F-fluciclovine (FACBC) and ⁶⁸Ga-PSMA-11 (PSMA) PET/CT scans for localizing prostate cancer (PCa) early biochemical recurrence (BCR) after radical prostatectomy (RP) (NCT02940262).

Methods: Fifty consecutive patients with BCR and prostate specific antigen (PSA) levels ranging from ≥0.2 to ≤2.0 ng/mL without any prior salvage therapy were included. All patients underwent FACBC and PSMA PET/CT scans within ≤15 days. PET/CT scans were each interpreted by 3 independent blinded expert readers not involved in study design and data acquisition. Region consensus interpretation (T,N,M1a,M1b,M1c) was generated based on majority rule in cases of reader disagreement (2 vs 1). PET/CT scans were considered as positive if any region was rated as positive . Detection rates per-patient and per-region served as primary study endpoint.

Results: Median time interval between the 2 scans was 6 days (range 1-15). Median PSA level at the time of imaging was 0.50 ng/ml (mean 0.63; range 0.2-2.0 ng/ml). The detection rates were significantly lower with FACBC than with PSMA PET/CT for the pelvic region (N) (8% vs 30%; p=0.003), for any extra-pelvic lesions (M) (0% vs. 16%; p=0.008) and per-patient (26% vs 56%; p=0.003). Reader agreement for PSMA PET/CT image interpretations was significantly higher than for FACBC PET/CT by patient (p=0.015) and region (p<0.001 to 0.046) based analysis.

Conclusions: In patients with BCR and low serum PSA levels after RP, PSMA PET/CT has higher detection rates and better reader agreement than FACBC PET/CT. Therefore, PSMA PET/CT should be the imaging modality of choice in patients with early BCR.

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