Should imaging surveillance be performed for a patient with CSPC on ADT with a single metastatic lesion to the pelvic bone?

Imaging Surveillance for CSPC Patient with Single Pelvic Bone Metastasis on ADT

Regular imaging surveillance should be performed in patients with castration-sensitive prostate cancer (CSPC) on androgen deprivation therapy (ADT) with a single metastatic lesion to monitor disease response/progression. 1

Recommended Imaging Protocol

Initial Baseline Assessment

• Complete contrast-enhanced CT scan of chest, abdomen, and pelvis with ≤5mm axial slices 1
• Bone scintigraphy (bone scan) to document baseline bone disease 1
• Consider whole-body MRI if available, particularly for better characterization of bone metastasis 1

Surveillance Schedule

1. First Year:

   • Imaging every 3-4 months with:
     • CT chest/abdomen/pelvis with contrast
     • Bone scan

2. Subsequent Years (if stable):

   • Imaging every 6 months 1
   • More frequent imaging if PSA rises or new symptoms develop

Rationale for Regular Imaging

The ESMO clinical practice guidelines explicitly state that "in patients with CRPC on systemic treatment, regular imaging studies should be done to monitor disease response/progression" 1. While your patient is currently castration-sensitive, the principles of monitoring metastatic disease remain similar.

Key reasons for regular imaging surveillance:

1. Early Detection of Progression: Patients with oligometastatic disease (single metastasis) can progress to polymetastatic disease, which impacts treatment decisions and prognosis

2. PSA Limitations: PSA alone is not sufficient to monitor response in metastatic prostate cancer, as discordance between PSA and radiographic findings can occur 1

3. Treatment Optimization: Early detection of progression allows for timely treatment modifications that can improve outcomes

Choice of Imaging Modalities

CT Scan

• Useful for detecting visceral metastases and lymphadenopathy 1
• Can detect sclerotic bone metastases but less sensitive than bone scan or MRI 1
• Should include chest imaging as lung metastases are relatively frequent in advanced disease 1

Bone Scan

• Standard for bone metastasis assessment 1
• Important to be aware of potential "flare phenomenon" after treatment initiation, which could be falsely interpreted as progression 1

Advanced Imaging Considerations

• Whole-body MRI provides superior assessment of bone metastases compared to conventional imaging 1
• PET/CT (with newer tracers like C-11 choline) may be considered if available, particularly if disease progression is suspected despite negative conventional imaging 1

Clinical Pitfalls to Avoid

1. Relying solely on PSA: PSA alone is insufficient to monitor metastatic disease. The ACR guidelines emphasize that imaging is necessary even when PSA is stable 1

2. Misinterpreting treatment response: Successfully treated bone metastases may become more sclerotic on CT, which can be falsely interpreted as disease progression 1

3. Overlooking soft tissue metastases: Up to 44% of patients with castration-resistant disease have soft tissue metastases, and 30% may have no bone involvement despite having metastatic disease 2

4. Neglecting bone health monitoring: Patients on ADT should also have bone mineral density monitoring due to increased risk of osteoporosis and fractures 1

Special Considerations for Oligometastatic Disease

Your patient with a single metastatic lesion represents oligometastatic disease, which may have a more favorable prognosis than widespread metastases. However, this status can change over time, making surveillance particularly important.

The pattern of progression (growth of existing lesion vs. development of new lesions) provides important prognostic information 1, making detailed imaging assessment valuable for treatment planning.

In conclusion, regular imaging surveillance is essential for monitoring disease status in patients with metastatic CSPC on ADT, even with a single bone metastasis, to optimize treatment decisions and improve outcomes.