Prostate-specific antigen (PSA) is a protein produced by the prostate gland in men. Levels are often elevated in men with prostate cancer, which is why a PSA test has long been used as a screening for prostate cancer.
However, before considering this test it’s important to be aware of its limitations. The PSA test was actually initially approved as a method to monitor the progression of prostate cancer in men who had already been diagnosed. Later, the US Food and Drug Administration approved it as a prostate cancer test in conjunction with a digital rectal exam.
Health organizations have long recommended that men begin yearly PSA screening at the age of 50, or even at 40 or 45 if a high risk of prostate cancer was present. This is now controversial, however, in large part because many benign prostate conditions can also cause PSA levels to rise. So while an elevated PSA test may indicate prostate cancer, it could also be due to:
- Prostatitis (inflammation of the prostate)
- Benign prostatic hyperplasia (BPH, or enlargement of the prostate)
- Urinary tract infection
- Prostate trauma (such as a prostate biopsy, catheter or even riding a bike)
- Sex/ejaculation (may lead to a mild, temporary increase in PSA)
- Age (PSA levels tend to increase gradually with age)
It used to be believed that a PSA level of 4.0 ng/mL or lower was normal. However, it’s now known that men may have prostate cancer even if their PSA is below 4.0 ng/mL, or conversely may be cancer-free even with higher levels. According to the National Cancer Institute:
“Most men with an elevated PSA level turn out not to have prostate cancer; only about 25 percent of men who have a prostate biopsy due to an elevated PSA level actually have prostate cancer.”
There is another consideration as well, which is that detecting prostate cancer early may not reduce your chances of dying from the disease. PSA tests may lead to over-diagnosis or overtreatment of small tumors that grow so slowly they’re unlikely to cause harm over a man’s lifetime.
Treating a prostate tumor unnecessarily could lead to unnecessary side effects from the cancer treatment, such as urinary incontinence or erectile dysfunction.
At this point, most experts agree that screening should be done on a case-by-case basis, and men should discuss with their physician whether or not a PSA screening test makes sense for them. In some cases, it may also be useful to monitor PSA levels over time. Dr. Samadi, chairman of Urology and Chief of Robotic Surgery at Lenox Hill Hospital, said in a press release:
“At the Dr. Samadi Prostate Cancer Center, our key approach is measuring the trend and velocity of the PSA over time. PSA mapping by a prostate cancer expert is the best way to determine if elevations are a cause for concern.
A PSA level of 4.0 ng/mL is normal, while changes of more than 2.0 ng/mL over the course of a year could be an indicator of the presence of prostate cancer. But an elevated PSA must be weighed against specific prostate cancer risk factors such as age, family history and lifestyle habits.”
CNBC September 8, 2015
National Cancer Institute, Prostate-Specific Antigen (PSA) Test