Prostate (Less Than) Specific Antigen
The PSA test is officially dead.
So declares the United States Preventive Services Task Force, a collection of experts who have been pouring over this issue for years. The serum prostate specific antigen (better known as PSA) is a laboratory test developed over 25 years ago and is widely used to screen men for prostate cancer. The Task Force publically concluded the lack of value of the PSA test in its press release in early October.
For those of us who have followed the debate about the use of PSA for screening the asymptomatic population the conclusion by the Task Force comes as little surprise. For several years now we’ve seen one study after the next call into question the value of a test that was touted as critical only a few years ago (Time magazine even ran an issue in 1996 dedicated to the PSA test; on the cover was a picture of General Schwarzkopf as a cancer survivor and high-profile advocate).
The prostate gland is nothing but trouble for elderly men and seems to serve no useful purpose beyond offering the afflicted individual the opportunity to get up and stretch his legs every couple of hours at night. Prostate enlargement (BPH) is the benign form of glandular mischief (although the first word in benign prostatic hypertrophy might be argued by those with more severe flow restriction) and can be tempered with medication and surgical procedures.
The more vexing prostate malady is the evil cousin to BPH: prostate carcinoma. This is the one that the PSA was meant to detect. The problem is that there are other things that can falsely elevate the PSA (such as BPH, obesity, and advanced age) and some early-stage prostate cancer can exist with a normal PSA level. To make matters worse, when the PSA test actually picks up an early case of prostate cancer we’re often not really sure what to do about it. Most prostate malignancies grow so slowly that the person has ample time to die from something else before the cancer finally gets them. It is estimated that nascent cancer is present in 30% of males in their forties and 70% of men over 80.
Add to this the fact that surgery to eliminate the cancer is not without its own set of problems. Up to half of men treated for prostate cancer develop impotence, urinary incontinence, or both. The death rate from prostate surgery is about 0.5% in the first 30 days.
For all these reasons we now have a panel of experts dictating that PSA should not be part of any routine screening for low-risk individuals. End of story, right?
Here’s another story. A colleague of mine (whose narrative I use with his explicit permission) requests a PSA as part of his yearly health screening and is shocked to discover a marked elevation. Further investigation reveals the presence of prostate cancer. Fortunately the malignancy has been diagnosed in an early enough stage that he should be cured with prostate surgery and won’t have to go through chemotherapy. This man is still young and at the peak of his career with many more years of life ahead to enjoy with his family and in his practice. Had he not undergone a PSA screening he would have harbored a quietly growing carcinoma that may have reached a point where its budding cells decided to take a trip through his blood stream to set up camp in his bones or brain. By that point the cat would be out of the bag.
So, which story is more compelling? We have scientifically rigorous studies showing that any advantage we gain by detecting prostate cancer early (with the PSA) is negated by the harm we inflict by unnecessarily removing the prostates of men who would have otherwise never been harmed by their malignancy. On the other hand, there is no dearth of testimonials from people who claim that their lives were saved by the application of this simple screening test. Would these people have survived even if they had never discovered the cancer? Would some of them—those who now suffer from incontinence and impotence—be healthier and happier if the cancer had remained undetected, growing so slowly that it never reaches a problematic stage?
What does my colleague do with the information he has? Can he not act on it? Is it really possible to accept the coldly analytical perspective of the Task Force’s new guidelines if you know that you fall into the category of people who’d be better off not knowing, and therefore receiving no therapy? I know I couldn’t.
What we are witnessing with this dilemma is the collision of population-based science on the one hand and the treatment of individual patients on the other. I confess that my beliefs are a perfect example of this illogical dichotomy. I have read the studies on which the Task Force’s recommendations are based and believe that their conclusions are correct: we really shouldn’t be doing PSA measurements on asymptomatic individuals. At the same time I believe (with equal fervor) that my colleague did the right thing by both asking for the PSA and acting on its results.
As humans it is in our nature to survive, and in the modern world where physical perils no longer involve starvation or getting eaten by saber-tooth tigers, our drive for self-preservation leads us to look for ways to prevent the predators that lurk within. For 25 years we’ve had what we believed was an easy and reliable way to detect early prostate cancer and now we’re being told that our beloved PSA assay is unhelpful when applied to the aggregate society.
Coming to a better understanding of the limitations of the PSA assay will undoubtedly help us focus our efforts on finding other ways to screen for prostate cancer in the future. This knowledge will allow us to move beyond a test that may not have served us as well as we’d hoped and, as with any other type of scientific discovery, is a first step in finding a new way forward.
I just wish it didn’t feel like a step backward.