The short answer
Biochemical recurrence means a rising PSA, not proven metastatic disease. Doubling time drives urgency, definitions differ after surgery and radiation, and PSMA PET now finds disease earlier.
Biochemical recurrence means a blood test has changed; it is not the same as having metastatic disease found on a scan.
After prostatectomy the usual threshold is a PSA of 0.2 ng/mL or higher, confirmed on a repeat test.
After radiation the standard is a rise of 2 ng/mL or more above the lowest value reached, called the Phoenix definition.
PSA doubling time matters more than any single value: a rise doubling in under six to nine months signals more urgency than a slow climb.
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The full explanation.
What a rising PSA actually means
After treatment for prostate cancer, PSA is checked at set intervals. When it starts to rise, that is called biochemical recurrence. It means a blood test has changed. It does not mean cancer has been found anywhere on a scan. It is not the same thing as metastatic disease.
That distinction is the single most useful thing to hold onto. Biochemical recurrence signals that some prostate cells making PSA are still present somewhere. For a good number of men, those cells never go on to cause symptoms or shorten life. For others they do, and nothing on this page can tell you which you are. That depends on your original pathology, how fast the PSA is moving, how long after treatment it started, your other health and your age. The next few months of testing are there to work out which group you are in.
The definitions differ by treatment
After radical prostatectomy, the gland is gone, so PSA should become essentially undetectable. Biochemical recurrence is generally defined as a PSA of 0.2 ng/mL or higher, confirmed on a second test. That figure comes from the American Urological Association, not from NCI, and some centres act on a lower or a rising ultrasensitive value, so ask which your team uses.
After radiation therapy, the prostate is still in place and still makes some PSA. So an undetectable level is not expected. The standard definition is a rise of 2 ng/mL or more above the lowest value reached. That lowest value is called the nadir, and this is the Phoenix definition, agreed at an ASTRO and RTOG consensus meeting. It was written to define recurrence for research, and clinicians do not wait for it before acting when the picture is clearly changing.
Because the thresholds differ, PSA numbers after surgery and after radiation are not directly comparable. Neither are the timelines.
PSA bounce
After radiation, PSA sometimes rises for a while and then falls again on its own. This is most common after brachytherapy. It is called a bounce. It happens more often in younger men, and it typically happens within the first two years. It is not recurrence. So do not react to one number. Ask whether a repeat test is the next step, before anything else happens.
PSA doubling time is what drives urgency
Not all rising PSAs behave alike. The most useful measure is how fast it is rising. That is PSA doubling time, worked out from several values over time.
A slow rise, doubling over many months or years, generally suggests indolent disease, meaning slow-growing cancer. It often supports continued monitoring. A rapid rise, doubling in under six to nine months, suggests more aggressive disease. It usually prompts faster imaging and a treatment discussion. The absolute PSA level matters too. So does your original Gleason grade, your surgical margins, and how long after treatment the rise began.
This is why your team may ask you to repeat PSA at intervals rather than acting on the first abnormal value. It is not delay. The trajectory carries more information than any single point.
PSMA PET changed what can be seen
For years, conventional bone scans and CT found almost nothing at low PSA levels. That left men in an unsatisfying gap, where a test was abnormal but imaging was blank.
PSMA PET imaging changed that. These scans use a tracer that binds prostate-specific membrane antigen. They detect disease at far lower PSA levels than conventional imaging. The FDA approved gallium-68 PSMA-11 in 2020 and piflufolastat F-18 in 2021.
This has real consequences. A PSMA PET may show a single spot that targeted radiation can treat. It may show nodes that change the plan. It may show nothing at all. Detection rates rise with higher PSA and faster doubling time. That is why the timing of the scan matters, and why a negative scan at very low PSA does not rule disease out.
What options generally follow
What comes next depends on your earlier treatment and on what imaging shows. The discussion may include salvage radiation to the prostate bed after surgery. It may include salvage local treatment after radiation, or targeted treatment of a small number of lesions. It may include hormone therapy, continued monitoring, or a clinical trial. Timing matters. Salvage radiation after surgery is generally more effective when it is given at a lower PSA level, which is the main reason your urologist may not want to watch a rising number for long. That is an argument against a long wait-and-see period in higher-risk situations.
There is no single correct answer. The trade-off between controlling disease and the side effects of further treatment is a legitimate part of the decision.
Worth asking
Ask what definition of recurrence your team is using, and what your doubling time is. Ask whether a PSMA PET is indicated now, or at a higher PSA. Ask what the goal of any proposed treatment is: cure, delay, or symptom prevention. And ask what happens if you do nothing for three months.
Sources
Words to know
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Common questions
Does a rising PSA mean the cancer has spread?
No. It means cells producing PSA are still present somewhere. For a good number of men those cells never go on to cause symptoms or shorten life, though that varies enormously between individuals. Imaging and the rate of rise are what distinguish situations that need action from those that do not.
Why is my team asking me to repeat the test instead of acting?
The trajectory carries more information than any single value. Several measurements over time allow PSA doubling time to be calculated, and a temporary bounce after radiation can otherwise be mistaken for recurrence. This is assessment, not delay.
Why is the threshold different after surgery and after radiation?
After prostatectomy the gland is gone, so PSA should be essentially undetectable and 0.2 ng/mL is meaningful. After radiation the prostate remains and keeps producing some PSA, so an undetectable level is never expected and the definition uses a rise above the lowest point reached.
What is a PSMA PET scan and should I have one?
It uses a tracer binding prostate-specific membrane antigen and detects disease at far lower PSA levels than conventional imaging. Gallium-68 PSMA-11 was FDA-approved in 2020 and piflufolastat F-18 in 2021. Detection rates rise with higher PSA and faster doubling time, so timing matters and your team can say whether now or later is more informative.
If nothing shows on the scan, what happens?
A negative scan at low PSA does not rule disease out. Options discussed may include salvage radiation to the prostate bed after surgery, hormone therapy, continued monitoring, or a trial. Timing matters, since salvage radiation after surgery is generally more effective at lower PSA levels.
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Written by: Cancer ExplainedSources last checked: 2026-07-30 what this meansLast updated: 2026-08-19Next planned review: 2028-07-30
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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