Are imaging surveillance recommendations for castration-resistant prostate cancer (CRPC) also applicable to patients with castration-sensitive prostate cancer (CSPC) on Androgen Deprivation Therapy (ADT)?

Imaging Surveillance Recommendations for Prostate Cancer: CRPC vs. CSPC

The imaging surveillance recommendations for castration-resistant prostate cancer (CRPC) are different from those for castration-sensitive prostate cancer (CSPC), with CRPC requiring more frequent and systematic imaging surveillance regardless of PSA levels.

Imaging Surveillance in CRPC

Recommendations for CRPC

• For patients with CRPC, regular imaging studies should be performed to monitor disease response/progression, as PSA alone is not a reliable indicator 1
• Conventional imaging should be integrated into monitoring disease status of men with non-metastatic CRPC (nmCRPC) at intervals of 6 to 12 months 1
• The exact interval for imaging should be determined by PSA doubling time (PSADT), development of symptoms, and patient/physician preference 1

Factors Affecting Imaging Frequency in CRPC

• Individual risk factors
• Age
• Overall patient health
• PSA velocity
• Gleason grade 1

Imaging Surveillance in CSPC

Current Recommendations for CSPC

• There are no specific imaging surveillance guidelines for CSPC patients on ADT in the absence of symptoms or rising PSA
• Unlike CRPC, where regular imaging is recommended regardless of PSA response, CSPC patients typically undergo imaging only when there is:
  • Rising PSA despite castrate testosterone levels
  • Development of new symptoms
  • Clinical suspicion of progression to CRPC

Rationale for Different Approaches

• CSPC has a more predictable response to ADT, with PSA generally being a reliable marker of disease status
• ADT significantly reduces visibility of castration-sensitive prostate cancer on imaging, particularly PSMA PET/CT 2
• In patients with CSPC who achieve PSA ≤2 ng/ml at 3 months after ADT initiation, median overall survival can be quite long (112 months in low-volume, low-risk disease) 3

Monitoring Transition from CSPC to CRPC

Key Indicators for Transition to CRPC

• Rising PSA with documented testosterone level <50 ng/dL (<1.7 nmol/L) on ADT 1
• Development of new symptoms despite castrate testosterone levels
• Radiographic progression despite ADT

When to Implement CRPC Imaging Protocols

• Once CRPC is confirmed, patients should receive laboratory assessment to confirm castrate testosterone levels 1
• Imaging tests should then be implemented to monitor for signs of distant metastases 1
• Serial PSA measurements should be obtained at 3-6 month intervals with PSADT calculation 1

Recommended Imaging Modalities

For Both CRPC and CSPC

• Conventional imaging:
  • CT scan with IV contrast for cancer detection and surveillance, particularly for visceral metastases 1
  • Bone scan for bone metastases 1
• MRI of the spine is recommended for patients with vertebral metastases to detect subclinical cord compression 1
• Urgent MRI of the spine is strongly recommended for patients with vertebral metastases and neurological symptoms 1

Common Pitfalls to Avoid

• Relying solely on PSA for disease monitoring in CRPC patients is inadequate 1
• Misinterpreting increased sclerosis on CT as disease progression when it may represent healing response to treatment 1
• Failing to recognize the flare phenomenon on bone scans after treatment initiation, which could be falsely interpreted as progression 1
• Not considering that ADT reduces visibility of castration-sensitive PC on PSMA PET/CT, potentially underestimating disease extent 2

Conclusion

The key difference in imaging surveillance between CRPC and CSPC is that CRPC requires regular, scheduled imaging regardless of PSA response, while CSPC generally relies on PSA monitoring with imaging performed when there is evidence of progression or development of symptoms. Once a patient transitions from CSPC to CRPC, the more intensive imaging surveillance protocol should be implemented.