64Cu-SAR-bisPSMA is safe and effective for detecting prostate-specific membrane antigen (PSMA)-expressing lesions, and 200MBq is the optimal dose for future clinical trials, according to research presented at the American Society of Clinical Oncology 2023 Annual Meeting.
In recent years, several new 68Ga- and 18F-based PSMA-targeted positron emission tomography (PET) agents have been approved by the US Food and Drug Administration to detect prostate cancer. These agents offer improved sensitivity and specificity compared with traditional imaging modalities.
Louise Emmett, MD, MBChB, FRACP, and colleagues designed the PROPELLER study to investigate 64Cu-SAR-bisPSMA, a novel imaging agent, in 30 men with untreated, histopathologically proven, primary prostate cancer with intermediate- to high-risk features. At screening, patients completed 68Ga-PSMA-11 PET/CT at 1 hour post-dose. After enrollment, patients received either 100MBq, 150MBq, or 200MBq of 64Cu-SAR-bisPSMA, followed by PET/computed tomography (CT) at 2 to 4 hours post-dose.
Researchers evaluated for safety before and after 64Cu-SAR-bisPSMA dosing. Two independent, blinded central readers evaluated the 68Ga-PSMA-11 and 64Cu-SAR-bisPSMA PET/CT scans for image quality, prostate cancer detection, and intensity of tracer uptake in identified lesions.
Reviewers scored 200MBq of 64Cu-SAR-bisPSMA as the dose providing the highest image quality, and only 1 grade 1 64Cu-SAR-bisPSMA-related adverse event was reported in the 200MBq cohort. In this cohort, 64Cu-SAR-bisPSMA and 68Ga-PSMA-11 were able to detect primary prostate cancer in 100% and 77.8% of patients for Reader 1 and 85.7% and 83.3% of patients for Reader 2, respectively.
Additionally, in the 200MBq cohort, 41 lesions with 64Cu-SAR-bisPSMA and 36 lesions with 68Ga-PSMA-11 were identified by Reader 1, while 31 lesions with 64Cu-SAR-bisPSMA and 22 lesions with 68Ga-PSMA-11 were identified by Reader 2.
Researchers also noted that in the 200MBq cohort, 64Cu-SAR-bisPSMA consistently showed higher uptake compared with 68Ga-PSMA-11.
Study authors concluded that 64Cu-SAR-bisPSMA is safe and effective for detecting PSMA-expressing lesions, with a 200MBq optimal dose, and shows a greater number of lesions that exhibited significantly higher uptake than 68Ga-PSMA-11 in men with intermediate- to high-risk prostate cancer. “Further studies to evaluate 64Cu-SAR-bisPSMA as an imaging agent in patients with biochemical recurrence of prostate cancer are underway,” they added.