What if a screening test shows an elevated PSA level?
If a man who has no symptoms of prostate cancer chooses to undergo prostate cancer screening and is found to have an elevated PSA level, the doctor may recommend another PSA test to confirm the original finding. If the PSA level is still high, the doctor may recommend that the man continue with PSA tests and DREs at regular intervals to watch for any changes over time.
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 transrectal 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 (transrectal 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?
Detecting prostate cancer early may not reduce the chance of dying from prostate cancer. When used in screening, the PSA test can help detect small tumors that do not cause symptoms. Finding a small tumor, however, may not necessarily reduce a man’s chance of dying from prostate cancer. Many tumors found through PSA testing grow so slowly that they are unlikely to threaten a man’s life. Detecting tumors that are not life threatening is called “overdiagnosis,” and treating these tumors is called “overtreatment.”
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 tumor that may have spread to other parts of the body before being detected.
The PSA test may give false-positive or false-negative results. A false-positive test result occurs when a man’s PSA level is elevated but no cancer is actually present. A false-positive test result may create anxiety for a man and his family and lead to additional medical procedures, such as a prostate biopsy, that can be harmful. Possible side effects of biopsies include serious infections, pain, and bleeding.
Most men with an elevated PSA level turn out not to have prostate cancer; only about 25% of men who have a prostate biopsy due to an elevated PSA level actually are found to have prostate cancer when a biopsy is done.2
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.
What research has been done to study prostate cancer screening?
Several randomized trials of prostate cancer screening have been carried out. One of the largest is the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, which NCI conducted to determine whether certain screening tests can help reduce the numbers of deaths from several common cancers. In the prostate portion of the trial, the PSA test and DRE were evaluated for their ability to decrease a man’s chances of dying from prostate cancer.
The PLCO investigators found that men who underwent annual prostate cancer screening had a higher incidence of prostate cancer than men in the control group but the same rate of deaths from the disease.3 Overall, the results suggest that many men were treated for prostate cancers that would not have been detected in their lifetime without screening. Consequently, these men were exposed unnecessarily to the potential harms of treatment.
A second large trial, the European Randomized Study of Screening for Prostate Cancer (ERSPC), compared prostate cancer deaths in men randomly assigned to PSA-based screening or no screening. As in the PLCO, men in ERSPC who were screened for prostate cancer had a higher incidence of the disease than control men. In contrast to the PLCO, however, men who were screened had a lower rate of death from prostate cancer.4,5
A recent paper analyzed data from the PLCO using a complicated statistical model to account for the fact that some men in the PLCO trial who were assigned to the control group had nevertheless undergone PSA screening. This analysis suggested that the level of benefit in the PLCO and ERSPC trials were similar and that both trials were consistent with some reduction in prostate cancer death in association with prostate cancer screening (6). Such statistical modeling studies have important limitations and rely on unverified assumptions that can render their findings questionable (or more suitable for further study than to serve as a basis for screening guidelines). More importantly, the model could not provide an assessment of the balance of benefits versus harms from screening.
The United States Preventive Services Task Force has analyzed the data from all reported prostate cancer screening trials, principally from the PLCO and ERSPC trials, and estimated that, for every 1,000 men ages 55 to 69 years who are screened every 1 to 4 years for 10 to 15 years:7
- About 1 death from prostate cancer would be avoided
- 120 men would have a false-positive test result that leads to a biopsy, and some men who get a biopsy would experience at least moderately bothersome symptoms from the biopsy
- 100 men would be diagnosed with prostate cancer. Of those, 80 would be treated (either immediately or after a period of active surveillance) with surgery or radiation. At least 60 of these men would have a serious complication from treatment, such as erectile dysfunction and/or urinary incontinence.
How is the PSA test used in men who have been treated for prostate cancer?
The PSA test is often used to monitor patients who have a history of prostate cancer to see if their cancer has recurred (come back). If a man’s PSA level begins to rise after prostate cancer treatment, it may be the first sign of a recurrence. Such a “biochemical relapse” typically appears months or years before other clinical signs and symptoms of prostate cancer recurrence.
However, a single elevated PSA measurement in a patient who has a history of prostate cancer does not always mean that the cancer has come back. A man who has been treated for prostate cancer should discuss an elevated PSA level with his doctor. The doctor may recommend repeating the PSA test or performing other tests to check for evidence of a recurrence. The doctor may look for a trend of rising PSA level over time rather than a single elevated PSA level.
READ FULL ARTICLE From National Cancer Institute