What Biochemical Recurrence Means
After treatment for prostate cancer, whether surgery (radical prostatectomy) or radiation therapy, your doctor monitors your PSA (prostate-specific antigen) levels through regular blood tests. PSA should drop to very low or undetectable levels after successful treatment. When it starts rising again, this is called biochemical recurrence.
Biochemical recurrence does not always mean the cancer has come back in a visible, dangerous way. But it is a signal that something is happening, and identifying the source of that rising PSA is critical for deciding what to do next.
The challenge has always been finding where the recurrence is. And for many years, conventional imaging struggled to answer that question early enough.
Why Conventional Scans Often Miss Early Recurrence
Traditional imaging methods used after prostate cancer treatment include CT scans, bone scans, and standard MRI. These are useful tools, but they have a significant limitation for detecting prostate cancer recurrence: they typically cannot detect disease at low PSA levels.
CT scans identify structural changes. A lymph node needs to be visibly enlarged before a CT scan flags it as suspicious. Bone scans detect changes in bone metabolism, but they require a certain disease burden before anything shows up. Standard MRI provides excellent soft tissue detail but still relies on visible anatomical changes.
For many men with biochemical recurrence, the PSA is rising from values like 0.2 to 0.5 ng/mL. At these levels, conventional scans frequently come back as “normal” or “no evidence of disease.” This leaves patients and their doctors in a difficult position: the blood test says something is happening, but the scans cannot show where.
How PSMA PET CT Changes the Picture
PSMA stands for prostate-specific membrane antigen, a protein that is expressed on the surface of prostate cancer cells. PSMA PET CT uses a radioactive tracer that binds specifically to this protein, lighting up prostate cancer cells wherever they are in the body.
This is fundamentally different from conventional imaging. Instead of looking for structural changes (a bigger lymph node, a visible bone lesion), PSMA PET CT looks for the cancer cells themselves. This molecular-level detection is why it can find recurrence at PSA levels where other scans see nothing.
Detection at Low PSA Levels
Research has consistently shown that PSMA PET CT can detect the site of recurrence in a significant proportion of patients with PSA levels below 1.0 ng/mL. Some studies report detection rates of 50 to 60 percent even at PSA levels between 0.2 and 0.5 ng/mL. As PSA rises above 1.0 ng/mL, detection rates climb further.
This early detection capability is clinically meaningful because treatment decisions made at lower PSA levels tend to have better outcomes. Finding a single site of recurrence in a pelvic lymph node, for example, opens up targeted treatment options that would not be considered if the recurrence location were unknown.
Whole-Body Coverage
PSMA PET CT scans the entire body in a single session. This means it can detect recurrence in the prostate bed (the area where the prostate was), regional lymph nodes, distant lymph nodes, bones, and even soft tissue metastases. Knowing the full extent and location of disease is essential for planning the right treatment approach.
What the Scan Involves
The PSMA PET CT scan itself is straightforward for patients. A small amount of the PSMA-targeting radioactive tracer is injected into a vein. After a waiting period (typically about 60 minutes) for the tracer to distribute and bind to PSMA-expressing cells, you lie on the scanner table while whole-body images are acquired. The scanning portion takes approximately 20 to 30 minutes.
There is no special fasting required for PSMA PET CT, unlike FDG PET CT scans which require sugar management. Your nuclear medicine centre will provide specific preparation instructions, but the process is generally well-tolerated.
What Happens After Detection
Finding the site of recurrence with PSMA PET CT directly influences treatment planning. The clinical approach depends on what the scan reveals.
Localised Recurrence
If the scan shows recurrence confined to the prostate bed (the area where the prostate used to be), salvage radiation therapy to that area is a common treatment option. PSMA PET CT helps radiation oncologists target their treatment more precisely.
Oligometastatic Disease
When the scan reveals recurrence in just one or a few spots (called oligometastatic disease), targeted approaches become possible. This might include stereotactic radiation to specific lymph nodes or metastases. The concept here is that treating a limited number of disease sites may delay or reduce the need for systemic therapy.
Widespread Disease
If PSMA PET CT reveals multiple metastatic sites, this guides the conversation toward systemic therapies such as hormone therapy, chemotherapy, or in some cases, PSMA-targeted radionuclide therapy (Lu-177 PSMA). The scan not only identifies the extent of disease but also confirms PSMA expression, which is relevant for determining eligibility for PSMA-targeted treatments.
When Should You Ask About PSMA PET CT?
If your PSA is rising after prostate cancer treatment and conventional scans have not identified the source, a conversation with your urologist or oncologist about PSMA PET CT is reasonable. This is particularly relevant if:
- Your PSA is rising progressively after surgery or radiation
- Previous CT scans and bone scans have been inconclusive
- Your treatment team is considering salvage therapy and needs to know the recurrence location
- You are being evaluated for targeted or systemic treatment options
Your doctor will assess whether PSMA PET CT is appropriate for your specific situation and what it might add to your clinical management.
A Significant Advance in Prostate Cancer Management
PSMA PET CT has changed the way prostate cancer recurrence is evaluated. By detecting disease at PSA levels where other scans are often negative, it fills a gap that has existed in prostate cancer management for decades. Earlier detection of recurrence location means earlier, more targeted treatment decisions.
If you or a family member is navigating prostate cancer follow-up and has questions about PSMA imaging, speak with your treating doctor about whether this scan is right for your situation. You can learn more about how we perform this scan on our PSMA PET CT scan page.