Intraindividual Comparison of ^99mTc-Methylene Diphosphonate and Prostate-Specific Membrane Antigen Ligand ^99mTc-MIP-1427 in Patients with Osseous Metastasized Prostate Cancer

Abstract

The objective of this study was to evaluate the rate of detection of bone metastases obtained with the prostate-specific membrane antigen (PSMA)-targeting tracer Tc-MIP-1427, as opposed to conventional bone scanning withTc-methylene diphosphonate (Tc-MDP), in a collective of patients with known advanced-stage osseous metastasized prostate cancer. Twenty-one patients with known metastatic disease were staged with both conventional bone scanning and PSMA ligand scintigraphy within a time frame of less than 10 d. Imaging included planar whole-body scanning and SPECT or SPECT/CT with 2 bed positions 3 h after injection of either 500-750 MBq ofTc-MIP-1427 or 600-750 MBq of Tc-MDP. Lesions were scored as typical tumor, equivocal (benign/malignant), or normal within a standard reporting schema divided into defined anatomic regions. Masked and consensus readings were performed with sequential unmasking: planar scans first, then SPECT/CT, the best evaluable comparator (including MRI), PET/CT, and follow-up examinations. Eleven patients had PSMA-positive visceral metastases that were predictably not diagnosed with conventional bone scanning. However, SPECT/CT was required to distinguish between soft-tissue uptake and overlapping bone. Four patients had extensive Tc-MDP-negative bone marrow lesions. Seven patients had superscan characteristics on bone scans; in contrast, the extent of red marrow involvement was more evident on PSMA scans. Only 3 patients had equivalent results on bone scans and PSMA scans. In 16 patients, more suspect lesions were detected with PSMA scanning than with bone scanning. In 2 patients (10%), a PSMA-negative tumor phenotype was present. PSMA scanning provided a clear advantage over bone scanning by reducing the number of equivocal findings in most patients. SPECT/CT was pivotal for differentiating bone metastases from extraosseous tumor lesions.

Chelation with a twist: a bifunctional chelator to enable room temperature radiolabeling and targeted PET imaging with scandium-44

“…In order to determine the binding affinity of both conjugates, we carried out the chemical synthesis of MIP-1427, a 99m Tc-radiolabeled, well-established PSMA-targeting imaging probe which has already been evaluated in patients. 32 , 50 Following successful synthesis, we carried out a radioactive displacement assay by challenging constant amounts of MIP-1427 with a varying concentration of non-radioactive Sc( iii ) complex. Non-radioactive DCFPyL was employed as an assay standard and to calculate relative K i 's based on the obtained IC 50 values.…”

Relationship between PSA kinetics and Tc‐99m HYNIC PSMA SPECT/CT detection rates of biochemical recurrence in patients with prostate cancer after radical prostatectomy

“…Although positron emitting radio nuclides labeling PSMA are widely used in the diagnosis and treatment of prostate cancer, Tc‐99m remains the radionuclide of choice for clinical scintigraphic imaging due to its favorable physical properties, low cost, and widespread availability . In addition, the radiation exposure from a single administration of a diagnostic dose is approximately 0.0046 mSv/MBq — similar to the radiation exposure from a conventional bone scan in nuclear imaging.…”

Keeping up with the prostate-specific membrane antigens (PSMAs): an introduction to a new class of positron emission tomography (PET) imaging agents

“…SPECT/CT with PSMA ligand 99m Tc-MIP-1427 was compared to conventional bone scans by Rathke et al in 21 patients with metastatic disease. The study showed an advantage for PSMA SPECT/CT, mainly by decreasing the number of equivocal findings and by its higher specificity, as it does not readily accumulate in degenerative bone disease ( 71 ).…”