Different Tracers Used in PSMA PET Scans
PSMA PET scans utilize several different radiotracers, with gallium-68 (68Ga) and fluorine-18 (18F) labeled compounds being the most common and clinically valuable options for detecting prostate cancer lesions. 1
Gallium-68 (68Ga) Based PSMA Tracers
68Ga-PSMA-11 (also known as HBED-CC) - One of the most widely studied and used PSMA tracers with FDA approval for detecting PSMA-positive lesions in men with prostate cancer who have suspected metastasis or recurrence based on elevated PSA levels 2
68Ga-PSMA-617 - Another gallium-based PSMA tracer that has shown utility in targeted radionuclide imaging and theranostics (diagnostic imaging combined with therapy) for metastatic prostate cancer 1
68Ga-PSMA-I&T (Imaging and Therapy) - A PSMA binding ligand used for both diagnostic imaging and potential therapeutic applications 1
Fluorine-18 (18F) Based PSMA Tracers
18F-DCFPyL (PYLARIFY) - A second-generation 18F-labeled PSMA agent that has demonstrated slightly higher sensitivity and better tumor-to-background ratios than 68Ga-PSMA-11 in comparative studies 1, 3
18F-PSMA-1007 - Shows greater local lesion detection capability due to its predominant hepatobiliary excretion pathway, which reduces urinary tract activity 4, 5
18F-DCFBC - An early 18F-labeled PSMA inhibitor particularly useful for detecting high-grade (Gleason 8-9) and larger primary tumors with minimal uptake in benign prostatic hyperplasia 1
18F-rhPSMA-7 - A newer PSMA tracer being evaluated in clinical studies 4
18F-AlF-PSMA-11 - Another emerging 18F-labeled PSMA tracer under investigation 4
Other PET Tracers Used in Prostate Cancer
11C-Choline - FDA approved in 2012 for imaging evaluation of men with biochemical recurrence of prostate cancer after definitive primary therapy; most useful when PSA > 2 ng/mL 1
18F-Fluciclovine (Axumin) - An amino acid analog PET radiotracer approved in 2016 for imaging evaluation of men with biochemical recurrence of prostate cancer 1
11C-Acetate - A lipogenesis radiopharmaceutical with high specificity (93%) for identifying the location of relapse, but limited by the short half-life (20.4 minutes) of 11C, requiring on-site cyclotron 1
18F-FDG - The most common PET radiopharmaceutical in oncology, but with limited utility in prostate cancer except in advanced metastatic castration-resistant disease 1
18F-FDHT - A ligand for androgen receptor that has shown usefulness for assessing androgen receptor blockade with second-line antiandrogens 1
Clinical Considerations for Tracer Selection
Half-life advantages: 18F-based tracers (110-minute half-life) offer logistical advantages over 68Ga-based tracers (68-minute half-life), allowing for centralized production and distribution to multiple imaging centers 1, 4
Detection sensitivity: PSMA-based tracers generally show superior diagnostic performance compared to conventional imaging and other PET tracers, particularly for biochemical recurrence at low PSA levels 1, 4
Excretion patterns: 18F-PSMA-1007 has predominantly hepatobiliary excretion, potentially improving detection of lesions near the urinary tract, while 68Ga-PSMA-11 has significant urinary excretion that may be mitigated with furosemide administration 4
False positives: 18F-PSMA-1007 has been associated with more benign bone uptake that could lead to false positives compared to 68Ga-PSMA-11 4
Practical Applications
For initial staging of intermediate to high-risk prostate cancer, PSMA PET tracers offer superior detection of metastatic disease compared to conventional imaging 1
For biochemical recurrence after definitive therapy, PSMA PET tracers can detect disease at lower PSA levels (0.2-0.5 ng/mL) than choline or fluciclovine-based tracers 1
For patient selection for PSMA-directed therapy, 68Ga-PSMA-11 is FDA-approved to identify appropriate candidates 2
For theranostic applications (combining diagnosis and therapy), 68Ga-PSMA-617 has shown particular utility 1