One of the hottest topics in advanced prostate cancer is prostate-specific membrane antigen (PSMA) scans and PSMA-targeted radionuclide therapy. PSMA is a type II membrane protein expressed in all forms of prostate tissue, including prostate cancer. PSMA sits on the surface of prostate cells and is heavily upregulated in prostate cancer, especially in metastatic and castration-resistant disease, making it a good target for scans and treatments.
At the 2019 ASCO virtual meeting, abstract 5013 was presented. The abstract described the association of noninvasive, radiographic measurement of prostate-specific membrane antigen (PSMA) expression with the response to PSMA-targeted radionuclide therapy (TRT). PJ Vlachostergios, MJ Niaz, SA Mosallaie, et al.
The study abstract referenced evaluated 216 men with metastatic CRPC who were treated with PSMA-targeted radionuclide therapy. The therapies included: 177Lu-J591 (n = 136), 177Lu-PSMA-617 (n = 38), Lu-J591 + Lu-PSMA-617 (n = 6), 225Ac-J591 (n = 7), and 90Y-J591 (n = 129).
Overall, 53.7% of men received low-dose treatment. By imaging, 74.5% of the subject men had high PSMA expression, which was associated with significantly more frequent PSA decline with the radionuclide therapies. There were 13 men with no PSMA uptake on their scans but still exhibited PSA declines when receiving PSMA target therapy.
In this first study to analyze PSMA-targeted radionuclide therapy response via imaging expression, the results demonstrated that the PSMA expression level is associated with response likelihood. However, negative imaging does not exclude all men who may benefit from PSMA therapy.
