For several months now, the prostate specific antigen (PSA ) test has been the subject of many headlines and news reports. The controversy has centered on the question of whether screening all men with the PSA test actually reduces the overall number of deaths from prostate cancer and whether the benefits of routine screening outweigh the risks.
There is no question that PSA screening can detect prostate cancer about 6 years earlier than a digital rectal exam and 5 to 10 years before symptoms of the disease are recognized. And statistics show that the prostate cancer mortality rate in the US has declined more than 40 percent since the early 1990s, when PSA screening became widespread.
But several large studies conducted to validate and quantify the effects of PSA screening have yielded divergent conclusions and strikingly different interpretations of the data on the part of physicians and scientists.
Though the matter has only recently been widely covered in the media, the physicians of the Urology Division have been investigating and discussing the implications on a daily basis since 2009, when preliminary reports of the studies were first published.
What is the prostate-specific antigen (PSA) test?
Prostate-specific antigen (PSA) is a protein produced by the cells of the prostate gland. The test, first approved by the FDA in 1986, measures the level of PSA in the blood. PSA tests, along with a digital rectal exam (DRE), are given to help detect or monitor prostate cancer.
What do the PSA test numbers mean?
Until recently, the PSA test has been almost uniformly recommended as a routine prostate cancer screening measure for men over age 50 or, for men considered to be at high risk for prostate cancer, beginning at age 40 or 45. The PSA test reveals the presence or absence of a marker for prostate cancer, it does not serve as a diagnosis of the disease. PSA results are reported as nanograms of PSA per milliliter (ng/mL) of blood. In general, most physicians have considered a total PSA level below 4.0 ng/mL as falling in the “normal” range. A higher concentration suggests an increased risk for the presence of prostate cancer. According to the American Cancer Society, levels between 4.0 and 10.0 ng/mL suggest approximately a 25 percent chance of prostate cancer, while men with levels above 10.0 ng/mL have about a 67 percent chance of prostate cancer being diagnosed upon further examination.
Urologists frequently employ a nuanced approach to PSA levels to increase the test’s usefulness as an individualized screening tool. For example, gauging “PSA velocity” — the change in PSA levels over a period of time—can contribute to a more precise estimate of the likelihood of cancer being present or a better understanding of the cancer’s aggressiveness.
Why is the PSA test controversial in screening?
The National Cancer Institute describes the PSA controversy as follows:
“Using the PSA test to screen men for prostate cancer is controversial because it is not yet known for certain whether this test actually saves lives. Moreover, it is not clear that the benefits of PSA screening outweigh the risks of follow-up diagnostic tests and cancer treatments.
For example, the PSA test may detect small cancers that would never become life threatening. This situation, called overdiagnosis, puts men at risk of complications from unnecessary treatment. The procedure used to diagnose prostate cancer (prostate biopsy) may cause harmful side effects, including bleeding and infection. Prostate cancer treatments, such as surgery and radiation therapy, may cause incontinence (inability to control urine flow), erectile dysfunction (erections inadequate for intercourse), and other complications. For these reasons, it is important that the benefits and risks of diagnostic procedures and treatment be taken into account when considering whether to undertake prostate cancer screening.”