When is a Prostate-Specific Membrane Antigen (PSMA) scan recommended for patients with suspected or confirmed prostate cancer?

PSMA Scan Recommendations for Prostate Cancer Patients

PSMA scans are recommended for patients with high-risk prostate cancer who have negative conventional imaging, and for patients with biochemical recurrence after definitive treatment with PSA levels ≥0.5 ng/mL. 1

Risk-Based Approach to PSMA Imaging

Initial Diagnosis and Staging

• Low-risk prostate cancer: PSMA scans are not recommended

  • No imaging is typically needed for patients with low-risk disease (T1/2, Gleason score 6, PSA <10 ng/mL) 1

• Intermediate-risk prostate cancer: Conventional imaging first

  • MRI or CT (abdomen and pelvis) and bone scan are recommended 1
  • PSMA scan may be considered for unfavorable intermediate-risk disease, though evidence is limited 1

• High-risk prostate cancer: Conventional imaging followed by PSMA scan if needed

  • Initial staging with bone scan plus either pelvic mpMRI or CT scan (strong recommendation) 1
  • If conventional imaging is negative but high suspicion for metastasis remains, PSMA PET/CT may be obtained (expert opinion) 1

Biochemical Recurrence

• PSMA scan recommended for PSA ≥0.5 ng/mL after definitive treatment 1
• Consider PSMA scan at lower PSA levels if patient is willing to undergo metastasis-directed therapy or seeking rationale to initiate systemic therapy 1

Clinical Benefits of PSMA Imaging

Improved Detection Accuracy

• PSMA PET/CT has 27% greater accuracy than conventional imaging in detecting nodal or distant metastasis in high-risk patients 1
• Higher sensitivity and specificity compared to bone scans and CT for detecting bone metastases 2, 3
• Can detect metastatic lesions missed by conventional imaging 4

Impact on Treatment Planning

• May influence treatment decisions such as:
  • Addition of systemic therapy
  • Implementation of metastases-directed therapy
  • Modification of radiation fields
  • Extent of surgical resection 1

Important Considerations and Limitations

Availability and Regulatory Status

• FDA has approved Gallium-68 PSMA-11 and piflufolastat F-18 PSMA (18F-DCFPyL) PET scanning for:
  • Initial staging for patients at high risk of metastasis
  • Evaluation of biochemical relapse after treatment 1

Clinical Benefit Uncertainty

• Despite improved staging accuracy, evidence for improved clinical outcomes based on PSMA-guided treatment modifications remains limited 1
• Identification of disease with molecular imaging may alter treatment, but the oncologic benefit of these alterations is still uncertain 1

Technical Considerations

• 18F-PSMA has advantages over 68Ga-PSMA including:
  • Longer half-life (110 vs 68 minutes)
  • Higher physical spatial resolution
  • Better logistics for transport and distribution 3

Practical Algorithm for PSMA Scan Use

1. Assess risk category of prostate cancer patient

2. For newly diagnosed patients:

   • If high-risk: Perform conventional imaging first (bone scan + CT/MRI)
   • If conventional imaging negative but high suspicion for metastasis: Consider PSMA PET/CT
   • If low or intermediate-risk: PSMA scan generally not indicated

3. For biochemical recurrence:

   • If PSA ≥0.5 ng/mL: PSMA scan recommended
   • If PSA <0.5 ng/mL: Consider PSMA scan if patient is candidate for metastasis-directed therapy

4. For M0 castration-resistant prostate cancer:

   • Consider PSMA scan when disease progression occurs and M1 disease treatments are being considered 1

By following this risk-stratified approach to PSMA imaging, clinicians can optimize detection of metastatic disease while avoiding unnecessary testing, ultimately improving patient outcomes through more precise treatment planning.