Prostate-specific membrane antigen (PSMA) fusion imaging in prostate cancer: PET–CT vs PET–MRI

Objectives: To investigate whether PET–CT or PET–MRI is more appropriate for imaging prostate cancer, in terms of primary tumor detection, local staging and recurrence, as well as lymph nodes and distant metastases. Methods: A systematic literature search was conducted on Embase, PubMed/MEDLINE, and the Cochrane Library database. Studies evaluating the diagnostic performance of PET–CT vs PET–MRI in prostate cancer patients were emphasized. Results: We reviewed 57 original research articles during the period 2016–2021: 14 articles regarding the radiotracer PSMA; 18 articles regarding the primary tumor detection, local tumor staging, managing local recurrence; 17 articles for managing lymph node metastases; and eight articles for managing bone and other distant metastases. PSMA PET could be complementary to mpMRI for primary prostate cancer localization and is particularly valuable for PI-RADS three lesions. PET–MRI is better than PET–CT in local tumor staging due to its specific benefit in predicting extracapsular extension in MRI-occult prostate cancer patients. PET–MRI is likely superior as compared with PET–CT in detecting local recurrence, and has slightly higher detection rates than PET–CT in lymph node recurrence. PET–CT and PET–MRI seem to have equivalent performance in detecting distant bony or visceral metastases. Conclusion: In conclusion, PET–MRI is suitable for local and regional disease, either primary staging or restaging, whereas PET–CT is valuable for managing distant bony or visceral metastasis. Advances in knowledge: We reviewed the emerging applications of PET–MRI and PET–CT in clinical aspects. Readers will gain an objective overview on the strength and shortfalls of PET–MRI or PET–CT in the management of prostate cancer.