THE PSA TEST
- The PSA test measures the blood level of PSA, a protein that is produced by the prostate gland. The higher a man’s PSA level, the more likely it is that he has prostate cancer. However, there are additional reasons for having an elevated PSA level, and some men who have prostate cancer do not have elevated PSA.
- The PSA test has been widely used to screen men for prostate cancer. It is also used to monitor men who have been diagnosed with prostate cancer to see if their cancer has recurred (come back) after initial treatment or is responding to therapy.
- Some advisory groups now recommend against the use of the PSA test to screen for prostate cancer because the benefits, if any, are small and the harms can be substantial. None recommend its use without a detailed discussion of the pros and cons of using the test.
What is the PSA test?
The blood level of PSA is often elevated in men with prostate cancer, and the PSA test was originally approved by the FDA in 1986 to monitor the progression of prostate cancer in men who had already been diagnosed with the disease.
In addition to prostate cancer, a number of benign (not cancerous) conditions can cause a man’s PSA level to rise. The most frequent benign prostate conditions that cause an elevation in PSA level are prostatitis (inflammation of the prostate) and benign prostatic hyperplasia (BPH) (enlargement of the prostate). There is no evidence that prostatitis or BPH leads to prostate cancer, but it is possible for a man to have one or both of these conditions and to develop prostate cancer as well.
Is the PSA test recommended for prostate cancer screening?
What is a normal PSA test result?
However, more recent studies have shown that some men with PSA levels below 4.0 ng/mL have prostate cancer and that many men with higher levels do not have prostate cancer. In addition, various factors can cause a man’s PSA level to fluctuate. For example, a man’s PSA level often rises if he has prostatitis or a urinary tract infection. Prostate biopsies and prostate surgery also increase PSA level. Conversely, some drugs—including finasteride and dutasteride, which are used to treat BPH—lower a man’s PSA level. PSA level may also vary somewhat across testing laboratories.
In general, however, the higher a man’s PSA level, the more likely it is that he has prostate cancer. Moreover, continuous rise in a man’s PSA level over time may also be a sign of prostate cancer.
What if a screening test shows an elevated PSA level?
If a man’s PSA level continues to rise or if a suspicious lump is detected during a DRE, the doctor may recommend additional tests to determine the nature of the problem. A urine test may be recommended to check for a urinary tract infection. The doctor may also recommend imaging tests, such as a trans rectal ultrasound, x-rays, or cystoscopy.
If prostate cancer is suspected, the doctor will recommend a prostate biopsy. During this procedure, multiple samples of prostate tissue are collected by inserting hollow needles into the prostate and then withdrawing them. Most often, the needles are inserted through the wall of the rectum (trans rectal biopsy); however, the needles may also be inserted through the skin between the scrotum and the anus (trans perennial biopsy). A pathologist then examines the collected tissue under a microscope. The doctor may use ultrasound to view the prostate during the biopsy, but ultrasound cannot be used alone to diagnose prostate cancer.
What are some of the limitations and potential harms of the PSA test for prostate cancer screening?
Overtreatment exposes men unnecessarily to the potential complications and harmful side effects of treatments for early prostate cancer, including surgery and radiation therapy. The side effects of these treatments include urinary incontinence (inability to control urine flow), problems with bowel function, erectile dysfunction (loss of erections, or having erections that are inadequate for sexual intercourse), and infection.
In addition, finding cancer early may not help a man who has a fast-growing or aggressive tumour that may have spread to other parts of the body before being detected.
The PSA test may give false-positive or false-negative results.
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.
A false-negative test result occurs when a man’s PSA level is low even though he actually has prostate cancer. False-negative test results may give a man, his family, and his doctor false assurance that he does not have cancer, when he may in fact have a cancer that requires treatment.