A new imaging agent has been found to be safe, fast, and efficient in visualizing metastatic prostate cancer, even in regions where the visualization is often challenging, such as bone and soft tissues.
The study, the results of a Phase 1/2a clinical trial (NCT01923727) in prostate cancer patients, was titled, “First-in-Human Imaging with 89Zr-Df-IAB2M Anti-PSMA Minibody in Patients with Metastatic Prostate Cancer: Pharmacokinetics, Biodistribution, Dosimetry, and Lesion Uptake,” were published in the Journal of Nuclear Medicine.
One of the dangers of cancer — including prostate cancer — is the ability of cancer cells to turn metastatic and spread elsewhere in the body.
To visualize cancer and possible metastasis, cancer cells need to be labeled in a way that allows them to be distinguished from normal cells. In general, florescent dyes are used for this purpose, but current visualization methods often have limitations, such as slow visualization time, toxicity, and low visualization in areas like bones and tissues.
A new imaging agent, a radiotracer called 89Zr-Df-IAB2M, was tested to see how well it aided scanning methods (positron emission tomography [PET] and computed tomography [CT]) in determining metastasis.
A total of 18 patients were injected with 89Zr-IAB2M at various doses: 6 were given 10 mg, another 6 at 20 mg, and the final 6 patients at 50 mg. They were then examined via PET and CT using the new imaging agent, and by conventional imaging approaches that include CT, a molecular bone scan, and PET with fluorodeoxyglucose, a common radiotracer. Select sites of suspected metastasis were also biopsied.
Results suggested that 89Zr-IAB2M is safe, as no side effects were experienced by the patients.
Equally important, 89Zr-Df-IAB2M was found to be useful in imaging skeletal and nodal lesions in 17 out of the 18 patients, visualized at 48 hours after injection. In total, 89Zr-Df-IAB2M helped to visualize 147 bone and 82 soft-tissue or nodal lesions, results that were superior to conventional methods.
“The radiotracer combines a small amount of the radioactive material zirconium-89 with a fragment of an antibody called a minibody. This minibody has anti-PSMA [prostate-specific membrane antigen] qualities and attaches to overexpression of the enzyme on the exterior of prostate cancer cells, wherever they may have traveled … Particles emitted from the site are then detected by positron emission tomography (PET). The resulting scan highlights ‘hot spots’ of PSMA overexpression,” Neeta Pandit-Taskar, MD, of the Memorial Sloan Kettering Cancer Center, said in a press release.
“Using this agent, we can detect the prostate cancer cells that have metastasized to bone — one of the most difficult areas to evaluate using standard methods,” she said, adding, “With further validation, this agent could potentially be used for targeted biopsies, which could lead to more appropriate, timely treatment for prostate cancer patients. It may also have potential use in targeted radiotherapy.”
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