Novel Theranostic Reagent Could Enhance Detection

A recently discovered prostate cancer selective antigen has been identified as a useful molecular imaging target for the detection and targeting of metastatic prostate cancer lesions, as reported in the November issue of the Journal of Nuclear Medicine. Using a new radiotracer, researchers were able to efficiently image STEAP1 (prostate six-transmembrane epithelial antigen-1) in tumors and localize a large number of lesions.

Metastatic castration-resistant prostate cancer (mCRPC) is a significant health problem, with more than 42,000 cases expected in 2020." Although significant progress has been made in detecting mCRPC with radiolabeled antibodies and small molecules that recognize prostate-specific membrane antigen (PSMA), other important potential targets, such as STEAP1, could be imaged to identify the presence of mCRPC and potentially serve as therapeutic targets,” said Jorge A. Carrasquillo , MD, who performed the study while an attending physician at Memorial Sloan Kettering Cancer Center in New York, New York."89Zr-DFO-MSTP2109 represents a new theranostic reagent that can both identify the extent of metastatic prostate cancer and to select patients for STEAP1-directed therapies."

The prospective, single-phase study included 19 patients with histologically confirmed progressive mCRPC with documented metastatic disease on bone scans, computed tomography (CT), or magnetic resonance imaging. Patients received approximately 185 MBq/10 mg of 89Zr-DFO-MSTP2109A and were imaged four to seven days post injection. Uptake and localization in the tumor were measured and compared with bone scans and CT. Bone and soft tissue biopsy specimens were also evaluated.

All patients imaged with 89Zr-DFO-MSTP2109A were considered positive for bone lesions, and eight patients were considered to have soft tissue disease. Localization of 89Zr-DFO-MSTP2109A in suspected bone metastases was observed in all patients; a total of 515 sites were recorded as positive. Bone injury analysis showed a median maximum SUV of 20.6, while a soft tissue injury analysis showed a median maximum SUV