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What PSA Really Means for Prostate Cancer

Summary & Participants

The PSA test remains a controversial screening tool for prostate cancer, but there is little doubt on its value for helping with treatment decisions. Learn what you need to know about PSA.

Medically Reviewed On: July 04, 2008

Webcast Transcript

ANNOUNCER: The detection of prostate cancer in the United States changed dramatically with the discovery of a screening technique based on a blood test for PSA. That stands for prostate specific antigen.

PHILIP KANTOFF, MD: The PSA is a protein. Its main function is in the prostate, in the semen; has no known function anywhere else in the body, but it's measurable in the blood. And there is an association between the level of the PSA in the blood and the likelihood of having prostate cancer.

ANNOUNCER: Previously, doctors could only screen for prostate cancer by feeling a hard lump in the gland. But this meant the cancer had to be relatively far advanced.

WILLIAM OH, MD: It really has changed the way we diagnose and treat this cancer. We are clearly seeing what's called a stage shift. That is, cancers are now diagnosed much earlier than they used to be, ten, fifteen years ago, because of PSA testing. And people have said that this is almost like a natural experiment in the United States, because the US led the way in screening.

ANNOUNCER: As men age, they often experience a non-cancerous growth in the size of their prostate called benign prostatic hyperplasia. This also elevates PSA levels in the blood. So there's some debate about when to send a patient to a surgeon for a biopsy, which is how prostate cancer is actually diagnosed.

ROBERT DREICER, MD: Over the last twenty years, there has been a lot of work trying to determine what a normal or abnormal level of prostate-specific antigen is. And for the early part, in the '80s and '90s, people used a cutoff of a value of 4 and said below that's normal and above that is abnormal; we know that that's actually not true. There are, in a sense, really no "normal" levels of PSA. There are ranges of PSA.

ANNOUNCER: For younger men, some doctors now say it is reasonable to be concerned when the PSA rises to 2.5.

PHILIP KANTOFF, MD: The normal level of PSA changes over a man's lifetime. So as men get older and older, the prevalence of benign prostatic hyperplasia increases, and generally men's glands increase, so the actual cutpoint of normal/abnormal changes as a function of age.

Generally speaking, what's the acceptable cutoff is 2.5 right now. So above 2.5 is considered an abnormal PSA.

Having said that, there are men who are older, in their 70s, where one might accept a level of 2.5 because the likelihood that that person's elevation in PSA is a result of benign prostatic hyperplasia is much higher and their likelihood of having prostate cancer is actually lower.

ANNOUNCER: Doctors are also interested in how the PSA level changes over time.

WILLIAM OH, MD: So, for example, a PSA that was rising very, very slowly over many years, even if the number itself was over 4, would be much less worrisome than a number that went from 2 to 4 in one year, for example.

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