How often will I have a PAMA (Positron Emission Tomography) PET scan while undergoing Lutetium-177 (LU-177) infusions?

Frequency of PSMA PET Scans During Lu-177 Therapy

During Lu-177 PSMA therapy, patients should undergo PSMA PET imaging at baseline before treatment initiation, after every 2 cycles of therapy (approximately every 12-16 weeks), and at least annually thereafter to monitor treatment response. 1, 2

Imaging Protocol for Lu-177 PSMA Therapy

Pre-Treatment Imaging

• Baseline PSMA PET scan: Required before initiating Lu-177 therapy to:
  • Confirm high PSMA expression in metastatic lesions
  • Ensure no dominant PSMA-negative metastatic lesions
  • Establish baseline disease burden for future comparison 2

During Treatment Monitoring

• Post-therapy imaging:

  • SPECT/CT imaging performed after each Lu-177 infusion (typically 1-24 hours post-infusion) to document radiopharmaceutical distribution 1, 3
  • Digital whole-body SPECT/CT scans can be completed in approximately 12 minutes and are well-tolerated by patients 3

• Response assessment imaging:

  • PSMA PET/CT recommended after every 2 cycles (approximately every 12-16 weeks) 1
  • For patients with nmCRPC (non-metastatic castration-resistant prostate cancer), imaging intervals of 6-12 months are suggested 1

Post-Treatment Monitoring

• Follow-up imaging:
  • At least annual PSMA PET/CT imaging even in the absence of PSA progression or new symptoms 1
  • More frequent imaging may be warranted with:
    • Rising PSA levels
    • Development of new symptoms
    • Shorter PSA doubling time 1

Treatment Regimen Context

• Standard Lu-177 PSMA therapy consists of:
  • 7.4 GBq (200 mCi) administered intravenously every 6 weeks
  • Typically 4-6 cycles of treatment 2
  • Time interval between cycles: 6-12 weeks 1

Clinical Considerations

Importance of Regular Imaging

• In the PREVAIL trial, 24.5% of patients had radiographic progression without PSA progression, highlighting the importance of routine imaging regardless of PSA values 1
• Quantitative analysis of post-therapy SPECT/CT images can predict treatment response, with >30% reduction in Lu-PSMA positive total tumor volume associated with improved survival 3

Treatment Response Assessment

• Response evaluation includes:
  • Changes in PSMA uptake on PET imaging (RECIST 1.1 criteria)
  • PSA response (≥50% decline observed in 57-66% of patients)
  • Clinical symptoms (pain relief, quality of life) 2, 4

Practical Considerations

• Digital whole-body SPECT/CT scans are well-tolerated, with 89% of scans successfully performed on the same day as treatment 3
• Treatment decisions for subsequent cycles may be modified based on imaging findings, particularly if there is evidence of disease progression or unexpected toxicity

Remember that while this represents the standard imaging protocol, individual adjustments may be necessary based on specific clinical circumstances, treatment response, and institutional protocols.