Detection Efficacy of (68)Ga-PSMA-11 PET/CT in Biochemical Recurrence of Prostate Cancer with Very Low PSA Levels: A 7-Year, Two-Center “Real-World” Experience

SIMPLE SUMMARY: Men with biochemical recurrence of prostate cancer (BCR) have increasing prostate-specific antigen (PSA) levels after potentially curative treatment, e.g., radical prostatectomy. Promptly finding these patients’ sites of recurrence potentially allows earlier, better-targeted treatment. Gallium-68 prostate-specific membrane antigen-11 positron emission tomography/computed tomography ((68)Ga-PSMA-11 PET/CT) imaging effectively localizes recurrence. However, this procedure’s detection rate of lesions suspicious for prostate cancer increases along with patients’ PSA levels, and limited published data describe performance when PSA is very low. We analyzed two academic institutions’ ~7-year “real-world” experience with (68)Ga-PSMA-11 PET/CT in 115 prostatectomized men with BCR with very low PSA (≤0.2 ng/mL). Altogether, 44 suspicious lesions (median [minimum–maximum] 1 [1–4]/patient) were found in 29/115 men (25.2%). Multiple lesions were detected in 9/115 (7.8%) at PSA concentrations as low as 0.03 ng/mL. (68)Ga-PSMA-11 PET/CT thus appears to be useful even in BCR with very low PSA. ABSTRACT: In biochemical recurrence of prostate cancer (BCR), prompt tumor localization guides early treatment, potentially improving patient outcomes. Gallium-68 prostate-specific membrane antigen-11 positron emission tomography/computed tomography ((68)Ga-PSMA-11 PET/CT) detection rates of lesions suspicious for prostate cancer are well known to rise along with prostate-specific antigen (PSA) concentration. However, published data are limited regarding very low values (≤0.2 ng/mL). We retrospectively analyzed ~7-year “real-world” experience in this setting in a large post-prostatectomy cohort (N = 115) from two academic clinics. Altogether 44 lesions were detected in 29/115 men (25.2%) (median [minimum–maximum] 1 [1–4]/positive scan). The apparent oligometastatic disease was found in nine patients (7.8%) at PSA as low as 0.03 ng/mL. Scan positivity rates were highest when PSA was >0.15 ng/mL, PSA doubling time was ≤12 months, or the Gleason score was ≥7b (in 83 and 107 patients, respectively, with available data); these findings were statistically significant (p ≤ 0.04), except regarding PSA level (p = 0.07). Given the benefits of promptly localizing recurrence, our observations suggest the potential value of (68)Ga-PSMA-11 PET/CT in the very low PSA BCR setting, especially in cases with more rapid PSA doubling time or with high-risk histology.