After Surgery and Radiation fail - New Hope - Gallium-68 PSMA as an imaging agent in prostate cancer recurrence

68Ga-PSMA PET/CT (a, b) and PET/MRI (c, d)images in patient 3. This is an example of the potential of MRI to clarify even moderate PSMA tracer accumulations visible on PET/CT. Tracer accumulation is visible on the PET/CT image (a yellow arrow) without correlation on the CT image (b), but pathological signals are visible on the PET/MR image (c white arrows) with correlationon the MR image (d white arrows) indicating bone metastases. a PET/CT fusion image, b CT image without contrast medium, c PET/MRI fusion image, d MR image (T1 with contrast medium and fat saturation)

Comparison of PET/CT and PET/MRI hybrid systems using a 68Ga-labelled PSMA ligand for the diagnosis of recurrent prostate cancer: Initial experience

Prostate Cancer

PSMA (Prostate Specific Membrane Antigen) 

Some of the studies presented from other centers were also very interesting. For example, PSMA is a cell surface transmembrane glycoprotein that is over-expressed in prostate cancer cells and would appear to provide a rational target for diagnostic imaging and possible directed therapy. Multiple Gallium (Ga68) labeled PSMA probes (imaging agents) have been topic of study particularly in Germany for the last few years. Researcher from Germany, Dr. Frederick Giesel, presented his work on Gallium PSMA PET in pre-treatment staging prior to radiation therapy. His study found that in 26 of 56 (46.4%) patients the treatment plan was changed after Gallium-PSMA PET imaging. This study demonstrates the significant impact that PET imaging probes can have on the treatment selection of patients with primary prostate cancer.

Prospective Comparison of 18F-Fluoromethylcholine Versus 68Ga-PSMA PET/CT in Prostate Cancer Patients Who Have Rising PSA After Curative Treatment and Are Being Considered for Targeted Therapy

Abstract

In prostate cancer with biochemical failure after therapy, current imaging techniques have a low detection rate at the prostate-specific antigen (PSA) levels at which targeted salvage therapy is effective. ¹¹C-choline and ¹⁸F-fluoromethylcholine, though widely used, have poor sensitivity at low PSA levels. ⁶⁸Ga-PSMA (Glu-NH-CO-NH-Lys-(Ahx)-[⁶⁸Ga-N,N′-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N′-diacetic acid]) has shown promising results in retrospective trials. Our aim was to prospectively compare the detection rates of ⁶⁸Ga-PSMA versus ¹⁸F-fluoromethylcholine PET/CT in men who were initially managed with radical prostatectomy, radiation treatment, or both and were being considered for targeted therapy.
In patients with biochemical failure and a low PSA level, ⁶⁸Ga-PSMA demonstrated a significantly higher detection rate than ¹⁸F-fluoromethylcholine and a high overall impact on management.

Gallium-68 PSMA as an imaging agent in prostate cancer recurrence | THE "NEW" PROSTATE CANCER INFOLINK
what this study really seems to be telling us is that, like [¹¹C]choline, [⁶⁸Ga]PSMA is only reliably accurate in men whose PSA level is >2 ng/ml, and what we need are imaging agents that can reliably detect recurrent prostate cancer at PSA levels that are more like 0.2 ng/ml or lower.
On the other hand, [⁶⁸Ga]PSMA is a lot more stable than [¹¹C]choline, which means that at least it could be used at many different nuclear medicine centers, as opposed to having to be made, one dose at a time, to treat specific patients at specific clinics that have the manufacturing capability.

68Ga-PSMA-PET/CT in Patients With Biochemical Prostate Cancer Recurrence and Negative 18F-Choline-PET/CT. - PubMed - NCBI

68Ga-PSMA ligand PET/CT in patients with prostate cancer: How we review and report | Cancer Imaging | Full Text