PSA Numbers in Advanced Prostate Cancer: What They Mean

If you or a loved one has advanced prostate cancer, you know that prostate-specific antigen (PSA) numbers are a common topic of conversation with your care team. In fact, your PSA level is probably one of the most closely watched numbers on your lab report.

A change in your PSA number can signal that something has changed. But interpreting your results isn’t always simple.

“PSA levels are used in many different settings to make decisions about prostate cancer,” says urologic oncologist Zeyad Schwen, MD. “But what the number means depends on where you are in your treatment.”

Dr. Schwen explains what PSA levels can tell you about advanced prostate cancer.

What could high PSA levels mean?

PSA is a protein made in your prostate gland. A small amount normally circulates in your bloodstream. But higher numbers deserve a closer look.

Healthcare providers use a PSA blood test as one way to screen for prostate cancer. A higher-than-normal PSA count could point to cancer. But it’s far from a perfect test.

“It’s not a very specific test,” Dr. Schwen clarifies. “Your PSA can be elevated for many reasons besides cancer.” 

Among them:

• A benign (noncancerous) enlarged prostate
• Certain medications or medical procedures
• Infection
• Recent sexual activity

While no PSA level automatically means you have advanced prostate cancer, higher numbers can raise your provider’s suspicion. Healthcare providers typically recommend additional imaging, like a PET scan, to look for signs of advanced prostate cancer when PSA levels are 20 or higher.

PSA and advanced prostate cancer treatment

As important as your PSA number can be, it’s not the only thing your healthcare team looks at when managing advanced prostate cancer.

“We don’t like to put all of our decision-making into that number,” Dr. Schwen emphasizes.

Your providers will also consider:

• Whether symptoms like bone pain, fatigue or urinary problems are improving
• Imaging tests, like PET scans, bone scans or MRIs
• How quickly your PSA level changes over time (called PSA doubling time)
• Your overall health and response to treatment

Your healthcare team will continue monitoring your PSA number throughout treatment for advanced prostate cancer. But what they hope to see depends on the type of treatment you’re receiving.

PSA and surgery

Your prostate creates PSA. So, if you’ve had your prostate removed (prostatectomy), your PSA levels should become undetectable.

“If your PSA becomes undetectable and stays that way, that’s a sign that no additional treatment is needed,” Dr. Schwen says.

But even very small increases in PSA levels later on can be a sign that your cancer has returned. In many cases, PSA tests can find evidence of cancer recurrence — even before it shows up on imaging.

PSA and radiation and hormone therapy

PSA behaves differently after radiation therapy.

Unlike surgery, radiation leaves prostate tissue behind, so your PSA level doesn’t usually fall to zero. And if you’re also taking hormone therapy — which is common for advanced prostate cancer — interpreting your PSA becomes more complicated.

“Hormone therapy may mask the PSA response,” Dr. Schwen explains. “You’ll often see PSA levels fall quickly because androgen deprivation therapy (ADT) lowers testosterone. That’s an expected response, but by itself, it doesn’t tell us how successful the treatment will be over the long term.”

That’s why your care team won’t rely on that initial drop alone if you’re on hormone therapy.

Instead, they’ll continue monitoring your PSA over time to see how low it goes and whether it stays low after you’ve completed hormone therapy.

PSA and metastatic prostate cancer

If prostate cancer has spread far beyond your prostate, your PSA number remains an important way to monitor how well treatment is working.

Most people with metastatic prostate cancer receive long-term hormone therapy, often combined with other medications or radiation.

During treatment, providers hope to see PSA levels fall after treatment begins and then remain stable over time.

If your PSA levels begin rising again while you’re still taking hormone therapy, that may suggest the cancer has become castration-resistant. That means it’s found ways to keep growing despite low testosterone levels.

Fortunately, treatment is still available.

“There have been tremendous advances in treating advanced prostate cancer over the past decade,” Dr. Schwen encourages. “Many people can still live for years with a good quality of life, even with metastatic disease.”

Final thoughts

It can be easy to fixate on your PSA numbers, especially if you see them change from one appointment to the next. But your PSA is just one tool your healthcare team uses to understand how your cancer is responding to treatment.

“Your PSA number is incredibly valuable,” Dr. Schwen acknowledges. “But it’s one piece of a much bigger picture.”

Rather than focusing on one PSA result, pay attention to the trend and talk with your healthcare team about what those changes mean for you. And remember: Your PSA number matters, but they don’t tell the whole story.