EANM-SNMMI Joint Guideline for 68Ga-PSMA PET/CT

on 14.10.18

Highlights from 68Ga-PSMA PET/CT: Joint EANM and SNMMI procedure guideline for prostate cancer imaging: version 1.0:

  • Nearly all adenocarcinomas of the prostate demonstrate PSMA expression in the majority of primary and metastatic lesions.
  • PSMA expression increases in case of de-differentiated, metastatic, or hormone-refractory disease. The level of expression is a significant prognosticator for disease outcome.
  • The use of 68Ga-PSMA PET/CT for localization of recurrent prostate cancer is especially recommended in patients with low PSA values between 0.2 and 10 ng/mL. Higher sensitivities are noted in patients with shorter PSA doubling times and those with higher initial Gleason scores.
  • In patients with high-risk disease (Gleason score > 7, PSA > 20 ng/mL, clinical stage T2c – 3a) the likelihood of lymph node and bone metastases is increased.
  • A contrast-enhanced 68Ga-PSMA PET/CT can replace abdomino-pelvic CT for the detection of lymph node metastases.
  • Approximately 5% of all prostate cancers do not exhibit significant PSMA over-expression.
  • Normal and variable PSMA ligand uptake can be found in the following tissues: lacrimal gland, salivary glands, liver, spleen, small intestine, colon, and kidney.
  • Due to high background activity in the liver, potential liver metastases can be obscured. This is compounded by the observation that liver metastases tend to lose PSMA expression in advanced metastatic disease.
  • Increased PSMA expression can also be found in the neovasculature of non-prostate cancers such as colon cancer, esophageal cancer, thyroid cancer, lung cancer, renal cell carcinoma, and brain tumours, as well as in benign tissue.
  • An important pitfall is relevant PSMA ligand uptake in coeliac ganglia of the autonomic nervous system which is prone to be misinterpreted as retroperitoneal lymph node metastases.
  • PSMA expression is physiologically upregulated after the beginning of ADT. A similar reaction is hypothesized for the use of second-generation AR-targeted therapies (e.g. enzalutamide, abiraterone). Caution has to be taken when interpreting an increase (or potentially a decrease) in PSMA expression shortly after start of a new AR-targeted therapy.
  • The coefficient for effective dose from 68Ga-PSMA averages is 2.0 × 10-2 mSv/MBq, resulting in an average effective radiation dose of 3 mSv for an administered activity of 150 MBq.