New treatment using actinium-225 (225Ac)-labeled targeted alpha therapy provides hope for men with advanced-stage, metastatic castration-resistant prostate cancer (mCRPC). Individuals with this type of cancer have limited options for treatment due to the aggressive nature of the tumor, but the new treatment shows a green signal. In the featured article of The Journal of Nuclear Medicine's October issue, a research team report the establishment of a dosing regimen for 225Ac labelled targeted alpha therapy in patients with prostate specific membrane antigen (PSMA)-positive tumors.
"The idea of targeted alpha therapy is not completely novel," explains Clemens Kratochwil, MD, University Hospital Heidelberg in Germany. "However, in contrast to hundreds of preclinical research reports, the clinical experience is still very limited. Our current results present a milestone with regard to clinical translation, because we could demonstrate how preclinical knowledge can be applied to human beings."
The New Treatment Protocol
"We developed a treatment protocol that presents a promising trade-off between toxicity and anti-tumor activity of PSMA-directed targeted alpha therapy," says Kratochwil. "However, our current results present only a starting-dose that, on the one hand, has still to be optimized and, on the other hand, needs further studies to evaluate its efficacy. Ultimately, there could be a new treatment modality to improve symptomatic patients and/or prolong survival."
Looking ahead, Kratochwil states, "If PSMA-targeted alpha therapy keeps its promise, it may earn a significant place in therapeutic nuclear medicine. However, it is the nature of all molecular targeting therapies that they can only be effective if the target is sufficiently expressed in the tumors. Thus, molecular imaging by means of PSMA-PET/CT also has an important role as a stratification criterion, and the 'theranostic' concept [combining diagnostic imaging of a biomarker with precise therapy] may be an additional motivation to establish PSMA-PET/CT as a routinely available imaging modality."