PSMA-PET Challenges Current Prostate Cancer Staging

TOPLINE: 

Prostate-specific membrane antigen–positron emission tomography (PSMA-PET) detected metastatic disease in 46% of patients with high-risk prostate cancer previously classified as nonmetastatic by conventional imaging. Results were positive in 84% of patients, with polymetastatic disease found in 24% of cases.

METHODOLOGY:

• Recurrent nonmetastatic hormone-sensitive prostate cancer is characterized by increasing prostate-specific antigen (PSA) levels while naive or responsive to androgen deprivation therapy, without evidence of metastasis on conventional imaging.
• A post hoc, retrospective, cross-sectional analysis included 182 patients from four prospective studies conducted from September 2016 to September 2021, with participants having recurrent prostate cancer after radical prostatectomy, definitive radiotherapy, or salvage radiotherapy.
• Inclusion criteria encompassed PSA levels > 1.0 ng/mL after radical prostatectomy and salvage radiotherapy or > 2.0 ng/mL above nadir after definitive radiotherapy, PSA doubling time ≤ 9 months, and serum testosterone ≥ 150 ng/dL.
• Researchers at University of California, Los Angeles performed Gallium-68-PSMA-11 PET/computed tomography imaging with a median injection of 5.0 mCi and uptake time of 61 minutes, with 98% of patients receiving CT contrast.

TAKEAWAY:

• PSMA-PET findings were positive in 80% of patients after radical prostatectomy, 92% after definitive radiotherapy, 85% after radical prostatectomy and salvage radiotherapy, and 84% overall (153 of 182 patients).
• Distant metastatic disease was detected in 34% of patients after radical prostatectomy, 56% after definitive radiotherapy, 60% after radical prostatectomy and salvage radiotherapy, and 46% overall.
• Polymetastatic disease (≥ 5 lesions) was identified in 19% of patients after radical prostatectomy, 36% after definitive radiotherapy, 23% after radical prostatectomy and salvage radiotherapy, and 24% overall.
• According to the authors, these findings suggest that patients’ high-risk nonmetastatic hormone-sensitive prostate cancers are understaged by conventional imaging.

IN PRACTICE:

“In a cohort of patients with high-risk hormone-sensitive prostate cancer without evidence of metastatic disease by conventional imaging, PSMA-PET results were positive in 84% of patients, detected M1 disease stage in 46% of patients, and found polymetastatic disease in 24% of patients…The results challenge the interpretation of previous studies, such as the EMBARK trial, and support the evolving role of PSMA-PET for patient selection in clinical and trial interventions in prostate cancer,” the authors of the new paper wrote. “Further studies are needed to assess its independent prognostic value and use for treatment guidance.”

SOURCE:

This study was led by Adrien Holzgreve, MD, and Wesley R. Armstrong, BS, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles. It was published online on January 3 in JAMA Network Open.

LIMITATIONS:

The analysis included significantly fewer patients treated with combined radical prostatectomy and salvage radiotherapy than the original EMBARK trial (29% vs 49%). Patients in this study had a lower median PSA doubling time and serum PSA level at enrollment than those in the EMBARK study. The retrospective nature of this study precluded systematic baseline imaging that would be standard for clinical trial enrollment. Additionally, while PSMA-PET offers the best diagnostic accuracy for prostate cancer staging, it can produce false-positive findings, particularly in bone metastases, with a positive predictive value of 0.84% in biochemical recurrence.

DISCLOSURES:

Holzgreve reported receiving personal fees from ABX advanced biochemical compounds outside the submitted work. This study was supported by grants from the Deutsche Forschungsgemeinschaft, the Prostate Cancer Foundation, and the Society of Nuclear Medicine and Molecular Imaging. Additional disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.