April 28, 2007 -- An article in the current issue of the journal Urology illustrates some of the hopes and barriers related to advancing our abilities to diagnose prostate cancer accurately through screening tests at the earliest possible time.
This particular article reports information about a prostate cancer protein found in the blood called EPCA-2.
The research, performed at Johns Hopkins in Baltimore -- recognized as one of the leading prostate cancer treatment and research centers in the world -- demonstrates that this new marker appears to be more sensitive and specific in detecting prostate cancer compared to the widely used PSA test.
But the question remains whether or not this is a major advance in the screening and diagnosis of prostate cancer.
An Imperfect Tool
The problem with the PSA test, which the article notes has been around and widely used for more than 25 years, is that, although it does detect prostate cancer through a fairly simple and routine blood test, it nonetheless is not particularly specific to prostate cancer.
That means that it frequently picks up other prostate conditions such as benign, or noncancerous, enlargement of the gland.
Another issue with the PSA test is what is normal and what is abnormal in terms of the PSA level in the blood.
We used to say that a PSA value on the blood test that was less than four was OK. More recent research suggests that even lower levels can be associated with prostate cancer.
When determining a "normal" PSA, the doctor should be considering the age of the patient and the change in the PSA value over time.
What that means is that if a young man (for this discussion, that would be someone in their 40s or early 50s) has a PSA of two, that may be abnormal, while a PSA slightly more than four in an 80-year-old man may not be of much concern.
It would be great if we had another simple test that helped solve some of these problems and allowed us to focus on those men who actually have prostate cancer as opposed to doing further investigations and evaluations on many men who don't have prostate cancer.
After all, these tests are not simple, inexpensive or painless. They involve rectal ultrasounds, biopsies, discomfort and risk, and even then, they can miss a prostate cancer if the biopsy doesn't "hit" the cancer when it is performed.
The researchers report in this current study that their new test is, in fact, more accurate in diagnosing prostate cancer, and it may also distinguish whether the cancer is still in an early stage when it is confined to the prostate gland, or if it is more advanced when it has broken through the capsule that surrounds the gland.
New Hope for Detection?
The next logical question is whether this test is really as good as it seems. And if it really is a major advance, you might be asking how soon the test will be available.
The answer to the first question is we hope it is. The answer to the second question is we don't know.
Frequently, when these types of papers appear in the literature, there are great claims made that the new test is a major advance and many folks get very excited about them.
To the credit of the authors of the current report, they have made it very clear in their article that this is simply a preliminary report of a newly discovered protein-based test. They commented that the test itself was "tested" on highly selected patients and was not evaluated in a typical setting where the doctor is actually screening a man for prostate cancer.
Establishing the value of this test, therefore, must be done in the context in which the test is going to be used.
That will mean many men who do not have prostate cancer will have the new test done side by side with the standard PSA test. Then, the researchers will look at the outcomes of both tests and compare them to each other.
If the new test turns out to be more accurate than PSA, then it will be a major advance. But we must always bear in mind that it may not show value in the subsequent "real life" evaluation.
The fact is we simply don't know today, based on this initial report, whether or not this test is going to be better, as good as or even worse than PSA testing when it is put into a clinical trial.
Other Promising Tests on the Way
Trying to find cancer through a blood test has been an area of research interest for many years. We have actually had other tests besides the PSA test that have been used in monitoring cancer patients for some time.
So, the EPCA test reported here is new, but it is not alone. Many researchers seek protein markers in the blood that may lead us to screen and diagnose cancer at the earliest possible moment.
I have heard experts say that within the next decade, we will have methods available that will incorporate nanotechnology and will allow us to take a drop of blood, put it on a chip, send it to the lab, and diagnose disease long before a doctor could find evidence of that disease by more standard clinical tests.
Other experts have reported research where they can monitor levels of a cancer-related protein called VEGF in rats, and pretreat those animals before a cancer tumor can be clinically detected.
So, to me, what this new report represents is an exciting opportunity that may affect medical care in the future.
If the clinical research, which will undoubtedly follow this report produces positive results, it will certainly help us direct our attention to men who have a greater likelihood of having prostate cancer, instead of the more nonspecific approaches we have today with the less sophisticated PSA test.
But we can't diminish the value of the PSA test in apparently helping to reduce deaths from prostate cancer, and we still need to prove that the new test is actually better than the older PSA test.
So, as with so many other exciting developments I have discussed in this blog, we still have a way to go to really understand how much impact this new test will actually have on the diagnosis of men with prostate cancer.
We are simply not there yet.
Dr. Len Lichtenfeld is deputy chief medical officer for the American Cancer Society. You can view the full blog by clicking here.