PSMA-Targeted Positron Emission Tomography Imaging in Solid Tumors Other Than Prostate Carcinoma: An Update

Prostate-specific membrane antigen (PSMA) has been previously shown to be over-expressed on newly formed vessels of a wide variety of solid tumors other than prostate carcinoma. Accordingly, the potential role of PSMA-targeted positron emitting tomography for staging, restaging and prediction of response to PSMA-targeted treatment modalities, including ¹⁷⁷Lu-PSMA-617, in other solid tumor types is being explored. Results derived from currently available studies on the role of PSMA-targeted imaging in solid tumors other than prostate carcinoma are encouraging with amongst others evidence of improved diagnostic accuracy in patients suffering from clear cell renal cell carcinoma and adenoid cystic adenocarcinoma of the salivary gland when compared to standard of care imaging, leading to a change in patient management in a significant number of patients. Furthermore, in hepatocellular carcinoma and glioblastoma, the comparable diagnostic accuracy of PSMA-targeted PET imaging when compared to contrast-enhanced CT and MRI suggest a potential use of PSMA-targeted PET when findings derived from morphological imaging are doubtful. Also, high PSMA-targeted PET-ligand uptake has been identified in iodine refractory thyroid carcinoma lesions as well as in triple negative breast carcinoma, suggesting a potential role for PSMA-targeted therapy in these patient populations. Thus far published results warrant, however, confirmation by larger prospective studies additionally assessing the longitudinal impact on patient outcomes.