Endocrine Abstracts

Objectives: Copper-64 (⁶⁴Cu, T1/2=12.7 h; Eβ+ max =0.65 MeV (17.9%); Eβ− max =0.57 MeV (39%)) is suitable for in-vivo PET imaging. Prostate specific membrane antigen (PSMA) is significantly over-expressed in undifferentiated prostate cancer tissue. We report the initial molecular imaging results with ⁶⁴Cu-PSMA PET/CT in patients with prostate cancer.

Methods: ⁶⁴Cu labeled PSMA (mean administered radioactivity – 260 MBq) was administered to nine patients referred for restaging following elevation of PSA. Whole-body PET/CT (Biograph mCT Flow 64) was performed up to 17 h p.i. All ⁶⁴Cu-PSMA-positive lesions were counted and SUV_max recorded. Comparison was made with previous and concurrent imaging, and therapy response evaluation was performed according to RECIST/PERCIST.

Results: Seven (77.7%) patients had previous prostatectomy. Two (22.2%) patients had uptake in the prostate bed, suggestive of local recurrent disease. Lymph node metastases were seen in five (55.5%) patients. Skeletal metastases were detected in four (44.4%) patients. Two (22.2%) patients demonstrated no pathological tracer uptake, compatible with bio-chemical recurrence post-prostatectomy. Three patients had stable disease (SD), despite PSA increase. Progressive disease (PD) was observed in four (44.4%) patients, out of which, three were recommended ¹⁷⁷Lu-PSMA radioligand therapy (PRLT). No adverse effects were observed in any patient.

Conclusion: Molecular imaging with ⁶⁴Cu-PSMA PET has potential for prostate cancer staging, restaging, and ¹⁷⁷Lu-PRLT planning. High resolution images were obtained. Late imaging, up to 17 h.p.i., is possible due to the longer half-life of ⁶⁴Cu. ⁶⁴Cu can be produced centrally and distributed to distant centers without a cyclotron or where ⁶⁸Ga-generator facilities are not available. ⁶⁴Cu-PSMA was found safe for human use. Future applications as Theranostics ‘matched pair’ using beta-emitting Copper-67 maybe possible. Clinical studies directly comparing other PET radiopharmaceuticals, such as ⁶⁸Ga- or ¹⁸F- PSMA or ¹⁸F-Choline are warranted to establish the specific role of ⁶⁴Cu-PSMA PET imaging in patients with prostate cancer.