Hi, I'm Dr. Scholz. Let's talk about prostate cancer.
In this video, we're going to talk further about PSA. We've covered PSA as a blood test
to screen for prostate cancer in men that don't know they have any cancer and that's
a very important topic. We're going to cover a separate aspect of the PSA blood test. In
fact, two aspects. One is how PSA can be used for monitoring and one is how PSA can be used
for staging.
Let's first cover how PSA can be used to stage newly diagnosed prostate cancer. Staging is
critically important because depending on how serious the prostate cancer is the type
of treatment is going to be altered. Very mild prostate cancers can even be watched
without treatment. More aggressive cancers need various kinds of therapies.
There's a connection between how many cancer cells are in your body and how high the PSA
level is. In the staging world, PSA is broken down into three broad categories: From 0-10,
10-20, and above 20. Obviously, the higher numbers are the more serious ones. Larger
tumors make more PSA. PSA, of course, is not the only factor. We have Gleason score and
digital rectal exam and other factors which aren't covered in this video. Bottom line,
PSA is an excellent tool for staging, but it's not the only important component.
So, PSA has another useful role for men with prostate cancer and that is for determining
what's going on with the cancer after treatment. This is important, not only for monitoring
men who have had surgery or radiation, but it's also important for men that may be under
therapy with hormone treatment or chemotherapy treatment. So it turns out that PSA rises
or falls depending on whether the cancer is growing or regressing in response to treatment.
Let's be clear, after surgery or radiation the PSA is supposed to remain low and stable.
After surgery, it should be 0. But in men that have relapsed disease who will have detectable
PSA levels you can determine if a new treatment such as hormone therapy is working depending
on whether the PSA declines significantly after starting the treatment.
So PSA is rather unique in that other cancers, blood tests for other cancers, typically are
nowhere near as accurate as PSA. People are often surprised that PSA can be so useful
given that all the controversies that surround the whole PSA screening situation. But this
is different. PSA screening after treatment for monitoring response is very accurate and
very useful.
Now let's move quickly on and talk about PSA for monitoring men on active surveillance.
As it turns out, PSA monitoring for active surveillance is not particularly accurate.
Unfortunately, there's a lot of background noise, there can be inflammation in the prostate,
so experts typically rely on biopsies to make final determinations about the status of the
cancer. However, new information suggests that high-quality MRIs can substitute for
biopsies in men that are on active surveillance.
Now let's talk about hormone therapy for men who have relapsed disease. PSA for men on
hormone therapy should decline to undetectable levels and the failure for PSA to drop to
less than say .1 indicates early hormone resistance, a very serious development. So PSA monitoring
for men after hormone therapy is a very accurate way to determine the quality of response.
Lastly, let's talk about PSA testing in men on chemotherapy. How do you know if chemotherapy
is actually controlling the disease? There have been different thresholds, but most experts
agree that if there's a 30% or more decline in PSA after starting chemotherapy that translates
into longer survival.
So as you can see, PSA is an incredibly useful test. It has different roles and different
thresholds depending on the type of treatment that is being monitored.
In men with relapsing disease the PSA will be rising. The rate of rise is called the
PSA doubling time. Specifically, that means how long does the PSA take to go from 1 to
2 or from 2 to 4, or from 4 to 8. That interval, which can range from a month to more than
a year, is essential for determining how aggressively the cancer is behaving. So the most aggressive
relapses are those that only require 3 months or less to double. An intermediate category
would be— say—between 3 months and 8 months, 3 months, 9 months. If the PSA is doubly slowly—say—requiring
more than 9 months to double, that's a low-grade relapse. The reason this information is useful
is because more rapid relapses suggest more aggressive cancer and that certainly justifies
more aggressive treatment. So men that have very quick doubling times may require two
or three treatments in combination to try and achieve disease control or even possibly
a cure in some cases. At the other end of the spectrum, let's say the PSA doubling time
is over a year. In those situations, studies indicate that many men can be watched with
no therapy at all. If you do the projections, it would take more than 20 years for these
individuals to ever become ill.
Anytime you talk about PSA there's always the following disclaimer. Lab tests can be
wrong and PSA is always interpreted in a stream or in a context of previous levels. Trends
are much more important than any single value. If you get a number that doesn't seem to fit
with previous trends, it should always be repeated.
Just to summarize, PSA for screening remains controversial for a variety of good reasons.
PSA after diagnosis is a precise and accurate test that doctors rely upon heavily to determine
the best treatment for you.
To learn more about prostate cancer staging, monitoring, and treatment check out the PCRI
Staging Guide at PCRI.org
Thanks for watching!
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