When to perform a PSAPET (Prostate-Specific Antigen Positron Emission Tomography) CT scan on a patient newly diagnosed with prostate cancer?

PSMA PET/CT Scan Indications for Newly Diagnosed Prostate Cancer

PSMA PET/CT scanning should be performed in newly diagnosed prostate cancer patients with high-risk disease features, while patients with low or favorable intermediate-risk disease generally do not require this advanced imaging. 1

Risk-Based Approach to Imaging

Low-Risk Disease

• Conventional imaging (bone scan, CT, MRI) is not recommended for asymptomatic patients with low-risk prostate cancer as the probability of nodal or distant metastasis is very low 1
• PSMA PET/CT is not indicated in this population due to low yield and unnecessary cost 1

Intermediate-Risk Disease

• For favorable intermediate-risk disease, conventional imaging is generally not necessary 1
• For unfavorable intermediate-risk disease, particularly with ISUP grade group 3 (Gleason 4+3=7), consider cross-sectional abdominopelvic imaging and bone scan 1
• PSMA PET/CT may be considered in unfavorable intermediate-risk patients if available, though evidence is still evolving 1

High-Risk Disease

• All patients with high-risk disease should undergo metastatic screening with PSMA PET/CT if available 1
• If PSMA PET/CT is not available, conventional imaging with bone scan plus either pelvic mpMRI or CT scan is strongly recommended 1
• High-risk features include: PSA >20 ng/mL, Gleason score ≥8, or clinical stage ≥T3 1, 2

Evidence Supporting PSMA PET/CT in High-Risk Disease

• PSMA PET/CT has demonstrated 27% greater accuracy than conventional imaging in detecting nodal and distant metastases in high-risk prostate cancer 1
• Sensitivity of PSMA PET/CT for nodal metastases is significantly higher than conventional imaging (85% vs 38%) 1
• Specificity is also superior with PSMA PET/CT compared to conventional imaging (98% vs 91%) 1
• PSMA PET/CT leads to management changes in approximately 28% of high-risk patients compared to 15% with conventional imaging 1

Clinical Decision Points

• For PSA <10 ng/mL with low-grade disease (Gleason ≤6), no imaging is typically needed 2
• For PSA 10-20 ng/mL, consider conventional imaging, especially with higher Gleason scores 2
• For PSA >20 ng/mL, PSMA PET/CT is strongly recommended if available; otherwise, bone scan and CT/MRI 2, 1
• Regardless of PSA, patients with Gleason score ≥8 or clinical stage ≥T3 should undergo PSMA PET/CT or conventional imaging 1

Practical Considerations

• PSMA PET/CT exposes patients to less radiation than conventional imaging (8.4 vs 19.2 mSv) 1
• PSMA PET/CT results in fewer equivocal findings (7% vs 23%) compared to conventional imaging 1
• FDA-approved options include Gallium 68 PSMA-11 PET scan and piflufolastat F-18 PSMA PET scan 3
• Detection rates for primary tumor with PSMA PET/CT vary by PSA level: 73% for PSA <5 ng/mL, 90% for PSA 5-10 ng/mL, and 97% for PSA >10 ng/mL 4

Common Pitfalls to Avoid

• Do not rely solely on PSA level for determining need for imaging; consider Gleason score and clinical stage 2
• Avoid unnecessary imaging in low-risk patients, which increases costs without clinical benefit 1
• Remember that small lymph node metastases below the spatial resolution of PET may still be missed 1
• Do not assume that negative conventional imaging definitively excludes metastatic disease in high-risk patients 1, 5