Imaging has transformed the way prostate cancer is diagnosed and staged. MRI scans of the prostate are now routine, and PSMA PET scans have become a powerful tool for checking whether cancer has spread. A growing body of evidence suggests that using the two together can improve diagnosis too. This article explains how combining MRI and PSMA PET works and what the PRIMARY trial found.
PSMA PET for staging
PSMA is a protein found in large amounts on the surface of most prostate cancer cells. A PSMA PET scan uses a small amount of a tracer that attaches to PSMA, making areas of cancer show up on the scan.
Since the proPSMA trial, led by Professor Declan Murphy and his team in Australia and published during the COVID-19 pandemic, practice has changed. Professor Dasgupta and his team now use a PSMA PET scan to check that there is no cancer outside the prostate before robotic prostatectomy in men with a Gleason score of 4+3 or above. This staging scan is far more accurate than the traditional bone scan, which was the standard for many years. Accurate staging matters because surgery is most effective when the cancer is confined to the prostate. Our robotic prostatectomy page explains the operation.
Can PSMA PET improve diagnosis as well?
The newer question is whether a PSMA PET scan can help diagnose prostate cancer when combined with an MRI of the prostate. The growing evidence suggests it can.
The PRIMARY trial found that combining MRI with PSMA PET increased the sensitivity for detecting significant prostate cancer from 83% to 97%. In other words, the combination missed far fewer cancers than MRI alone. Nothing in medicine is 100% accurate, but this is a significant improvement.
The trial was presented as a podcast and video by the British Journal of Urology International, a journal Professor Dasgupta was proud to edit for nearly a decade as its tenth Editor-in-Chief. You can watch the video below.
Who could benefit
The combination could be particularly valuable for men in whom cancer is suspected, for example because of a rising PSA, but does not show clearly on MRI. MRI scans are not perfect at ruling out prostate cancer, and our article on cancer after a negative MRI explains why follow-up still matters in that situation.
Combined imaging could also help some men avoid unnecessary biopsies, by giving greater confidence when both scans look reassuring. Biopsies are generally safe, but avoiding one where it is not needed spares discomfort and a small risk of complications.
Could some men skip a biopsy?
Much more controversial is whether some men could avoid a biopsy altogether. If an area that looks suspicious on MRI also shines brightly on PSMA PET, could treatment such as robotic prostatectomy go ahead without a biopsy? This is not yet standard practice, and further research is needed before it could be recommended.
Cost and insurance
Another practical question is whether insurers will cover the cost of PSMA PET scans as practice changes. Patients considering private care may wish to check this with their insurer before tests are arranged.
Where to find out more
Prostate Cancer UK explains the scans used in diagnosis and staging, and Cancer Research UK has information on how prostate cancer is diagnosed. Our overview of prostate cancer and our article on smart screening describe the wider pathway.
Clinically relevant results
The PRIMARY trial results are clinically relevant and important for patients. They point towards a future in which imaging finds significant cancers more reliably, while sparing men tests they do not need.
If you would like to discuss which scans might help in your case, please contact the clinic to arrange a consultation with Professor Dasgupta.