What are the EANM (European Association of Nuclear Medicine) guidelines for PSMA (Prostate-Specific Membrane Antigen) PET/CT (Positron Emission Tomography/Computed Tomography) scans?

EANM Guidelines for PSMA PET/CT in Prostate Cancer Imaging

The European Association of Nuclear Medicine (EANM) strongly recommends PSMA PET/CT as the first-line imaging modality for prostate cancer staging due to its superior accuracy (92% vs 65%), sensitivity (85% vs 38%), and specificity (98% vs 91%) compared to conventional imaging. 1, 2

Indications for PSMA PET/CT

• Primary staging:

  • Strongly recommended for high-risk localized/locally advanced prostate cancer 1
  • Recommended for intermediate-risk disease, particularly ISUP grade group 3 1
  • Not recommended for low-risk disease 1

• Biochemical recurrence:

  • Recommended for detection of recurrent disease and metastatic spread
  • Particularly valuable when conventional imaging is negative or equivocal 3

Patient Preparation

• Prior to scan:
  • Avoid androgen deprivation therapy (ADT) before imaging when possible, as it reduces visibility of prostate cancer lesions 4
  • Adequate hydration and forced diuresis recommended for PSMA ligands primarily excreted via kidneys 4
  • Document relevant clinical information:
    • PSA level and kinetics
    • Gleason score/ISUP grade
    • Previous treatments (surgery, radiation, ADT)
    • Results of prior imaging studies

Acquisition Protocol

• Radiopharmaceutical options:

  • 68Ga-labeled tracers: PSMA-11, PSMA-I&T, PSMA-617
  • 18F-labeled tracers: DCFPyL, PSMA-1007, rhPSMA-7, JK-PSMA-7 4

• Timing:

  • Standard acquisition: 60 minutes post-injection 5
  • Shorter acquisition times (45 min) show small but significant reductions in image quality 5
  • Late imaging (90-120 min) may help clarify unclear findings 4

• Image acquisition:

  • Whole-body scan from vertex to mid-thigh
  • Extended field of view to include lower extremities when clinically indicated

Image Interpretation

• Normal biodistribution:

  • Physiological uptake in salivary glands, lacrimal glands, liver, spleen, kidneys, small intestine, and urinary tract 4
  • Caution with 18F-labeled PSMA ligands that may show unspecific focal bone uptake 4

• Pathological findings:

  • Primary tumor: Focal uptake in prostate gland
  • Lymph node metastases: Focal uptake in pelvic or retroperitoneal lymph nodes
  • Bone metastases: Focal uptake in bone, typically corresponding to sclerotic lesions on CT
  • Visceral metastases: Focal uptake in liver, lungs, or other organs

Clinical Impact and Advantages

• Compared to conventional imaging:
  • Higher detection rates for lymph node metastases (sensitivity 75-77%, specificity 99%) 1, 2
  • Fewer equivocal findings (7% vs 23%) 1
  • Lower radiation exposure (8.4 vs 19.2 mSv) 1
  • More frequent management changes (28% vs 15%) 1

Limitations and Pitfalls

• False negatives:

  • Small lymph node metastases below spatial resolution of PET may be missed 1
  • Low PSMA expression in some prostate cancer subtypes
  • Prior ADT may reduce PSMA expression and visibility 4

• False positives:

  • PSMA expression in neovasculature of other solid tumors 4
  • Uptake in inflammatory lymph nodes 4
  • Unspecific bone uptake with some 18F-labeled tracers 4

Quality Control

• Regular quality control procedures are essential for optimal performance of PET/CT systems 6
• Follow EANM guidelines for routine quality control of PET-CT systems 6

PSMA PET/CT represents a significant advancement in prostate cancer imaging with demonstrated improvements in patient outcomes through more accurate staging and treatment planning.