The labeling of 99mtc-psma-hbed-cc for prostate cancer imaging

Abstract

Prostate cancer (PCa) is the second most common cancer and the fifth leading cause of death worldwide in 2018 (1). Initially, PCa diagnosis is based on Prostate Specific Antigen (PSA) blood test, which is low sensitivity and low specificity, and sonography guided needle biopsy, which is invasive. Therefore, molecular imaging recently enrolls as an important technique in PCa diagnosis using some small molecules which are well developed to bind to overexpressed Prostate Specific Membrane Antigen (PSMA). The small molecules, for example PSMA-HBED-CC, PSMA I&T, can be chelated with Ga-68 for diagnostic purpose using positron emission tomography (PET) scan. Even though PET scan provides good contrast and spatial resolution, the related cost is high. Meanwhile, single photon emission computed tomography (SPECT) imaging offers more affordable with longer half-life of radiotracer. Therefore, it is difficult for most patients to access to PET scan in limited PET facilities. Herein, we report a new tracer using Tc-99m labeled with PSMA-HBED-CC aim to be alternative option for PCa diagnosis. The purpose of this study was to develop in-house preparation of 99mTc-PSMA-HBED-CC for prostate cancer imaging using SPECT system. 99mTc-pertechnetate 370 MBq was added to mixture solution of PSMA-HBED-CC 10 µg and 4% SnCl2·2H2O in 10 mL sterile vial, then heated to 100 oC 15 minutes and incubated while cool down to room temperature. Labeling parameters were optimized to obtain the maximum radiochemical yield of 99mTc-PSMA-HBED-CC. The completeness chelation was determined by instant thin layer chromatography (iTLC) and pH of 99mTc-PSMA-HBED-CC was measured. 99mTc-PSMA-HBED-CC was successfully chelated using 99mTc-pertechnetate solution in high radiochemical yield (71.49%) and radiochemical purity (98.29%) which is sufficient to administer to patient for SPECT imaging of PCa diagnosis according to International Atomic Energy Agency (IAEA) recommendation.