Why all the controversy about PSA? How can people fault a simple blood test that uncovers cancer at an early stage? The problem is that the PSA test doesn't specify what type of cancer the patient has. In addition to the presence of cancer, there are two other common causes of PSA elevation—prostate gland enlargement that comes with age, called BPH, and chronic prostate inflammation, called prostatitis.
PSA by itself doesn’t diagnose prostate cancer. It is a nonspecific indicator, like the “check engine” light on the dashboard of your car.* Does this eliminate the value of PSA? Of course not. An elevated PSA reading is a useful indicator of the need for further research into the cause.
The biggest fear--and the primary argument used by PSA naysayers--is that so many urologists recommend immediate random biopsy with any PSA elevation whatsoever. A million men are biopsied annually in the US, resulting in the over-diagnosis of innocuous prostate cancers in about 100,000 men each year. Most of these men end up undergoing unnecessary radical surgery or radiation.
So how do we eliminate the bathwater (random biopsies) without throwing out the baby (PSA)? The first step is avoiding the trap of rushing headlong into something before learning the whole story. Since we know PSA is nonspecific, most elevations will be from prostate enlargement, not cancer. PSA needs to be interpreted in relation to prostate size.
One might think that only ultrasound or MRI can reliably measure prostate size. And while imaging is indeed the most accurate method, practiced doctors can roughly estimate prostate size with a simple digital prostate exam. Also, there is a PSA blood test variant called “free” PSA that is suppressed in men with BPH. Free PSA is reported out as a percentage of total PSA. When free PSA percentage drops below 10%, BPH as a cause for PSA elevation is less likely.
Sequential PSA testing is the best way to diagnose inflammatory prostatitis, the other common reason for benign PSA elevation. Inflammation can increase PSA, which often oscillates up and down as the inflammation in the gland waxes and wanes. This bouncing PSA pattern is in sharp contrast to an elevation of PSA caused by cancer. A rise in PSA from cancer is usually unidirectional—up, up and up.
Historically, despite the drawbacks from biopsy of over-diagnosis, infections and discomfort, it has been the gold standard for diagnosing prostate cancer. Only very recently have new advances in multiparametric MRI imaging enabled men with PSA elevation to consider this imaging alternative--rather than random biopsy--as a first step. Our recommendation to use a multiparametric MRI (at a center of excellence) followed by a targeted biopsy if a suspicious lesion is detected, has been discussed in more detail in previous blogs.
*I wish I could take credit for the check engine light idea that so nicely conveys the useful but nonspecific character of PSA. This little pearl of knowledge was passed on to me by a patient.