What it means
PSMA stands for prostate-specific membrane antigen, a protein on the surface of prostate cells. Most prostate cancers carry far more of it than normal tissue does. For a PSMA PET scan, a small amount of a radioactive tracer that sticks to PSMA is injected into a vein. Areas where it collects look bright and are called PSMA-avid. A CT or MRI taken at the same time shows exactly where they are.
When it matters
PSMA PET is used to see whether higher-risk prostate cancer has spread before treatment. It also looks for cancer that has come back when PSA rises after treatment. It can show small deposits that other scans miss, though a small fraction of cancers carry little PSMA. Not every bright spot is cancer: salivary glands, kidneys and bowel take it up normally, and benign changes like healing fractures can too. Strong uptake can also make PSMA-targeted treatment an option.
Questions to ask your doctor
- Are the PSMA-avid spots typical of prostate cancer, or could any be benign?
- Has the cancer spread outside the prostate, and if so, where?
- Does my scan show enough uptake for PSMA-targeted treatment?
