Synthesis and imaging of F-18 prostate specific membrane antigen-1007: institutional experience

Ga-68 PSMA is a widely used tracer for imaging disseminated prostate cancer patients. Ga-68 being a generator produced radionuclide has limitation of number of elutions per day. Rise in number of prostate cancer patients worldwide lead to development of F-18 PSMA for imaging prostate cancer in centres where number of patients are more. The present study aims to share the preliminary experience of F-18 PSMA-1007 synthesis and imaging in prostate cancer patients. F-18 was produced using O-18 as target material by p,n reaction in medical cyclotron. Radiosynthesis was done in cassette based automated module (ORA Neptis) using commercially available kit. After performing all the initial checks cassette was placed in the module. After passing the quality control tests of the cassette, reagents vial and precursor were placed at appropriate positions. C18ec and PS-H⁺ cartridges were used for purification. TBA was used as eluent. ITLC was performed on silica strip using 60% ACN as mobile phase. Apyrogenecity was tested using PTS system and sterility were tested by incubating the samples in fluid thioglycollate and soybeancasein medium at 370 C for upto 7 days. Wholebody PET/CT imaging was performed in total 15 patients at 45-60 min post IV injection of 7-8mCi of F-18 PSMA-1007. The total synthesis time was 40 min post F-18 delivery in module. Radiolabelling yield of 30-40% was achieved. Formulation was found to be sterile and endotoxin content was ranging from 1.98-2.75 EU/ml which is well below permissible limit (175 EU). Biodistribution of F-18 PSMA-1007 was found to be almost similar to Ga-68 PSMA. F-18 PSMA-1007 has reduced urinary clearance enabling assessment of the prostate. High target to background ratio was observed in both primary and metastatic lesions. ¹⁸F-PSMA-1007 performs at least comparably to Ga-68 PSMA, it also overcomes some practical limitations of Ga-68 labelled PSMA targeted tracers because of longer half-life combined with its superior energy characteristics and low urinary excretion. Due to high radiolabelling yield of ¹⁸F-PSMA-1007, multiple tracer syntheses per day is not required as it is needed in Ga-68 PSMA. ¹⁸F-PSMA-1007 can also be transferred to satellite centers. (author)