A novel single-photon emission computed tomography/computed tomography (SPECT/CT) acquisition method using lead (Pb)-212–prostate-specific membrane antigen (PSMA)-based targeted alpha therapy may provide convenient detection of radiopharmaceutical biodistribution and could lead to improved practice and increased accessibility among patients with prostate cancer, according to a recent study published by Griffiths et al in The Journal of Nuclear Medicine. The findings may lay the groundwork for more personalized treatments in prostate cancer.
Background
There has recently been interest in the development of Pb-212–PSMA-based targeted alpha therapy for patients with metastatic castration-resistant prostate cancer. However, Pb-212 is a challenging isotope to image because of the high-energy gamma rays that generate significant scatter.
“The ability to acquire imaging of an alpha-emitter with a standard SPECT camera and standard collimator within a convenient acquisition time for the patient could provide more precision in how we treat patients with prostate cancer and … other cancers in the future. Confirming the presence of the drug in the target is important, because it serves as a quality assurance and can be used to derive an understanding of the biodistribution and pharmacokinetics of the drug,” emphasized co–study author Stephen Rose, PhD, Head of Translational Medicine and Clinical Science at AdvanCell.
Study Methods and Results
In the recent study, researchers administered 60 MBq of Pb-212–ADVC001 to a 73-year-old male patient with metastatic castration-resistant prostate cancer. SPECT/CT imaging occurred at 1.5, 5, 20, and 28 hours following infusion.
The researchers found that representative Pb-212 SPECT/CT images demonstrated rapid tumor uptake of Pb-212–ADVC001 in agreement with the tumor burden shown on the pretreatment fluorine-18–DCFPyl PET/CT images. They noted the images acquired after 20 hours showed persistent tumor uptake despite low counts caused by Pb-212 decay.
Conclusions
“In the future, this imaging technique can help to streamline the drug development process, driving conviction in the agents we bring to larger scale trials. In addition, the ability to image Pb-[212] with a standard SPECT camera in a relatively short timeframe means that Pb-[212] is a true theranostic alpha-emitter and could be valuable in selecting patients for targeted alpha-therapies,” indicated Dr. Rose. “What’s more, access to PET imaging is a bottleneck in the United States and globally. SPECT cameras are more widely available and may address this critical issue, as SPECT imaging can be used for patient selection, therapy decision-making, and guiding adaptive dosing strategies based on changes of target expression and tumor volume during treatment,” he concluded.
Disclosure: Dr. Rose is an employee of AdvanCell. For full disclosures of the study authors, visit jnm.snmjournals.org.
