99mTechnetium Based PSMA-Radioguided Assisted Surgery for Prostate Cancer (TRACE) Feasibility Study

Given the difficulty visualizing lymph node involvement with pre-operative imaging alone, and the potential to miss metastatic nodal involvement on template PLND, radioguided surgery has been proposed as a technique to improve intra-operative detection and clearance. 99mTechnetium (99mTc) is a frequently used radioisotope in nuclear medicine, with favourable radiation properties and commercial availability[11]. It has a 6-hour half-life, and is suited to allow target tissue accumulation, while minimizing patients and investigator radiation exposure. Novel molecule-targeted radiopharmaceuticals using 99mTC and other radioisotopes in the setting of PC have increasing potential for diagnostic imaging, monitoring of therapeutic interventions and directed surgery[11, 12]. In relation to radioguided surgery, 99mTC -based PSMA-radioguided surgery (99mTc-PSMA-RGS) was deployed in a feasibility study. Using a specifically designed 99mTc based tracer, 99mTc-mas3-y-nal-k(Sub-KuE), or in short Tc-99m-PSMA I&S, combined with a gamma probe, guidance of the surgical resection of recurrent PC lymph node metastases was undertaken in 132 patients, yielding a sensitivity of 84% and specificity of 100% and detecting metastases as small as 3mm[15, 16]. This raises the question as to whether a combination of PSMA PET/CT imaging and PSMA-radioguided surgery may increase the cure rate in patients undergoing operative management of PC, by increasing detection sensitivity and specificity of nodal metastases.