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Seven Takeaways from Meta-Analysis of PSMA Radiotracers for Prostate Cancer Imaging
In a newly published meta-analysis of 24 studies, researchers noted that the PSMA PET radiotracer 18F PSMA-1007 may provide more benefit than 68Ga Ga-PSMA-11 for primary staging of patients with prostate cancer and detection of local lesion recurrence, but also has drawbacks with higher liver uptake and multiple reports of false positive bone lesions.
Are fluorine-18 (18F)-labelled PSMA PET/CT agents more advantageous than gallium-68 (68Ga) radiotracers for the diagnosis and management of patients with prostate cancer?
With this question in mind, the authors of a new meta-analysis, recently published in Prostate Cancer and Prostatic Disease, reviewed 24 studies with the majority of them comparing 18F PSMA-1007 and 68Ga Ga-PSMA-11. In the meta-analysis, the researchers examined use of the positron emission tomography (PET) radiotracers for primary staging of patients with prostate cancer (PCa), post-recurrence restaging, additional organ distribution and cost/production considerations.
Here are seven takeaways from the meta-analysis:
1. For primary staging, 18F PSMA-1007 provided better detection of focal prostate cancer (PCa) lesions and lymph node (LN) lesions in comparison to 68Ga Ga-PSMA-11. The meta-analysis authors noted that 18F PSMA-1007 had over a 14 percent higher sensitivity rate, an 8.5 percent higher negative predictive value (NPV) and similar accuracy for local PCa lesions in contrast to 68Ga Ga-PSMA-11, according to one prospective comparative analysis. However, the same analysis noted a 7.3 percent higher specificity rate and a 9.3 percent higher positive predictive value (PPV) for 68Ga Ga-PSMA-11.
2. In a 2021 prospective comparative study for the detection of recurrent PCa, researchers found that 18F PSMA-1007 had double the sensitivity rate of 68Ga Ga-PSMA-11 as well as a 16.7 percent higher specificity rate and a 14.7 percent higher accuracy rate.
3. Citing a 2022 study that examined local PCa lesion detection after biochemical recurrence, the meta-analysis authors noted that 18F PSMA-1007 had consistently higher detection rates than 68Ga Ga-PSMA-11 across PSA levels ranging from 0.2 ng/mL to 5 ng/mL. They noted that the biggest difference between the radiotracer agents (15.4 percent) occurred with patients at the lowest PSA levels (0.2-0.5 ng/mL) with 18F PSMA-1007 detecting 52.9 percent of local lesions vs. 37.5 percent for 68Ga Ga-PSMA-11.
4. Noting reports of false positive bone lesions with 18F PSMA-1007 in multiple studies, the meta-analysis authors cautioned that an analysis of three studies found that 18F PSMA-1007 had a significantly higher benign bone SUVmax in comparison to 68Ga Ga-PSMA-11.
5. In contrast to 68Ga Ga-PSMA-11, 18F PSMA-1007 had nearly double the mean liver SUVmean in one study and more than double the liver uptake in two other studies, according to the meta-analysis authors. The researchers cautioned that the higher liver uptake with 18F PSMA-1007 may obscure adjacent metastatic lesions.
6. The meta-analysis authors also noted “significantly lower urinary bladder uptake” for 18F PSMA-1007 in multiple studies with one study noting a nearly fivefold reduction and another study documenting a greater than sixfold reduction in comparison to 68Ga Ga-PSMA-11.
(Editor’s note: For other content on prostate cancer imaging, see https://www.diagnosticimaging.com/clinical/prostate-cancer .)
7. In their examination of production and cost considerations with the radiotracer agents, the meta-analysis authors noted a number of challenges for the use of 68Ga Ga-PSMA-11. These challenges include a short half-life, the need for an on-site generator and lower production yield, which may negatively impact image resolution. One advantage with 68Ga Ga-PSMA-11 is streamlined labeling with automated systems at ambient temperature whereas the majority of 18F-based PSMA radiotracers need manual labeling with specific temperature requirements, according to the meta-analysis authors.
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