SNMMI 2019: PSMA PET During Lu-177–PSMA Radioligand Therapy May Help Guide Treatment
Prostate-specific membrane antigen (PSMA) positron-emission tomography (PET) imaging of patients with metastatic castration-resistant prostate cancer after two cycles of lutetium-177 (Lu-177)-PSMA radioligand therapy has shown a significant predictive value for patient survival. The research was presented at the 2019 Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI) and published by Gaftia et al in The Journal of Nuclear Medicine.
In phase II trials, Lu-177–PSMA therapy has shown promising results in treating patients with metastatic castration-resistant prostate cancer. The therapy typically involves a preliminary PSMA PET scan to identify patients who are eligible for the treatment. While interim PET scans have shown high predictive value for patients with lymphoma, this concept has not been previously explored in patients with prostate cancer undergoing Lu-177–PSMA therapy.
Study Methods
The retrospective analysis was conducted at Klinikum rechts der Isar hospital, Technical University Munich, Germany, and included patients who underwent gallium-68–PSMA11 PET/computed tomography (CT) at baseline and after two cycles of Lu-177–PSMA radioligand therapy under a compassionate use program.
Instead of standardized uptake value—which is the parameter generally used in such analyses—researchers used qPSMA, an in-house developed software, to evaluate the whole-body tumor burden.
Findings
“Tumor response was assessed by the changes in PSMA-avid tumor volume from baseline to the second PSMA PET using three classification methods,” explained first study author Andrei Gafita, MD. “Subsequently, we found that tumor response assessed on interim PSMA PET after two radioligand therapy cycles was associated with overall survival.”
Dr. Gafita stated, “Our results therefore show that interim PSMA PET can be used for therapeutic response assessment in patients undergoing [Lu-177–PSMA] radioligand therapy. Furthermore, occurrence of new lesions in PSMA PET is a prognostic factor for disease progression and could be included in defining tumor response based on PSMA PET imaging.”
“While further analyses involving clinical parameters are warranted,” Dr. Gafita added, “this analysis paves the way for use of interim PSMA PET in a prospective setting during [Lu-177–PSMA] radioligand therapy.”
Disclosure: For full disclosures of the study authors, visit jnm.snmjournals.org.
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