How is it used?
If prostate cancer is diagnosed, the total PSA test may be used as a monitoring tool to help determine the effectiveness of treatment. It may also be ordered at regular intervals after treatment to detect recurrence of the cancer.
The total PSA test and digital rectal exam (DRE) may be used to screen both asymptomatic and symptomatic men for prostate cancer. If either the PSA or the DRE are found to be abnormal, then the doctor may choose to follow this testing with a prostate biopsy and perhaps imaging tests, such as an ultrasound. If the DRE is normal but the PSA is moderately elevated, the doctor may order a free PSA test to look at the ratio of free to total PSA. This can help to distinguish between prostate cancer and other non-cancer causes of elevated PSA. Since the total PSA test can be elevated temporarily for a variety of reasons, a doctor may order another PSA a few weeks after the first to determine if the PSA is still elevated.
Currently there is no consensus about using the PSA test to screen for prostate cancer in asymptomatic men. While prostate cancer is a relatively common type of cancer in men, it is an uncommon cause of death. In cases where the cancer appears to be slow-growing, the doctor and patient may decide to monitor its progress rather than pursue immediate treatment (called “watchful waiting”). Total PSA levels may be ordered at intervals to monitor the change in PSA over time.
The complexed PSA (cPSA) is a relatively new test that may be ordered, along with the DRE, as an alternative to the total PSA. There is hope that this test could be more specific than the total PSA – better at detecting cancer-related PSA, but findings have been mixed and its ultimate clinical utility has yet to be established. The cPSA is an option that doctors can discuss with their patients. Its use may expand and/or be better defined as additional studies are conducted and findings are reported.
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When is it ordered?
There is currently no consensus among the experts about when the PSA test should be ordered to screen asymptomatic males. Over-diagnosing, identifying cases of prostate cancer that may never cause significant health problems, must be balanced against missing the detection of aggressive cancers.
National organizations reflect this lack of consensus, giving conflicting recommendations on routine PSA-based screening of asymptomatic men. Some organizations such as the American Urological Association recommend screening, while others such as the U.S. Preventive Services Task Force feel that the harms associated with over-diagnosis and over-treatment outweigh the potential benefits. The American Cancer Society (ACS) recommends that men discuss the advantages and disadvantages of PSA-based screening for prostate cancer with their doctor before making an informed decision about whether to be screened or not.
For men who wish to be screened, the ACS recommends that healthy men of average risk consider waiting to get tested until age 50; for those at high risk, such as American men of African descent and men with a family history of the disease, the recommendation is to consider beginning testing at age 40 or 45. The American Urological Association recommends a baseline PSA and DRE at age 40. (See Screening Tests for Adults (30-49): Prostate cancer and Screening Tests for Adults (50 and Up): Prostate cancer for details on screening recommendations.)
The total PSA test and DRE may also be ordered when a man has symptoms that could be due to prostate cancer, such as difficult, painful, and/or frequent urination, back pain, and/or pelvic pain. Since these symptoms are seen with a variety of other conditions, including infection and prostatitis, the doctor will also frequently order other tests, such as a urine culture. Some of these conditions can themselves cause temporary increases in PSA levels. If a total PSA level is elevated, a doctor may order a repeat test a few weeks later to determine whether the PSA concentrations have returned to normal.
A free PSA is primarily ordered when a man has a moderately elevated total PSA. The results give the doctor additional information about whether the person is at an increased risk of having prostate cancer and help with the decision of whether to biopsy the prostate.
The total PSA may be ordered during treatment of men who have been diagnosed with prostate cancer to verify the effectiveness of treatment and at regular intervals after treatment to monitor for cancer recurrence. It is also ordered at regular intervals when a man with cancer is participating in “watchful waiting” and not currently treating his prostate cancer.
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What does the test result mean?
PSA test results can be interpreted a number of different ways and there may be differences in cutoff values between different laboratories. The normal value for total PSA is considered to be less than 4.0 ng/ml (nanograms per milliliter of blood). There are some that feel that this level should be lowered to 2.5 ng/ml in order to detect more cases of prostate cancer. Others argue that this would exacerbate over-diagnosing and over-treating cancers that are not clinically significant.
There is agreement that men with a total PSA level greater than 10.0 ng/ml are at an increased risk for prostate cancer (more than a 67% chance, according to the ACS). Levels between 4.0 ng/ml and 10.0 ng/ml may indicate prostate cancer (about a 25% chance, according to the ACS), BPH, or prostatitis. These conditions are more common in the elderly, as is a general increase in PSA levels. Concentrations of total PSA between 4.0 ng/ml and 10.0 ng/ml are often referred to as the “gray zone.” It is in this range that the free PSA is the most useful. When men in the gray zone have decreased levels of free PSA, they have a higher probability of prostate cancer; when they have elevated levels of free PSA, the risk is diminished. The ratio of free to total PSA can help the doctor decide whether or not a prostate biopsy should be performed.
When the complexed PSA (cPSA) test is used as a screening tool, increased levels may indicate an increased risk of prostate cancer, while lower levels indicate a decreased risk.
In addition to the introduction of the free PSA and cPSA tests, there have been efforts to increase the usefulness of the total PSA as a screening tool. They include:
- PSA velocity. This is the change in PSA concentrations over time. If the PSA continues to rise significantly over time (at least 3 samples at least 18 months apart), then it is more likely that prostate cancer is present. If it climbs rapidly, then the affected person may have a more aggressive form of cancer.
- PSA doubling time. This is another version of the PSA velocity. It measures how rapidly the PSA concentration doubles.
- PSA density. This is a comparison of the PSA concentration and the volume of the prostate (as measured by ultrasound). Men with larger prostates tend to produce more PSA, so this factor is an adjustment to compensate for the size.
- Age-specific PSA ranges. Since PSA levels naturally increase as a man ages, it has been proposed that normal ranges be tailored to a man’s age.
During treatment for prostate cancer, the PSA level should begin to fall. At the end of treatment, it should be at very low or undetectable levels in the blood. If concentrations do not fall to very low levels, then the treatment has not been fully effective. Following treatment, the PSA test is performed at regular intervals to monitor the person for cancer recurrence. Since even tiny increases can be significant, those affected may want to have their monitoring PSA tests done by the same laboratory each time so that testing variation is kept to a minimum.
A relatively new test called “ultrasensitive PSA” (USPSA) has been reported. It has been suggested that this test may be useful in monitoring for persistence or recurrence of cancer after treatment. This test detects PSA at much lower levels than the traditional test. It has been suggested that increases in PSA due to the persistence or return of cancer can be identified much sooner with this test. However, results of this test must be interpreted with caution. Because the test is very sensitive, there can be an increase in PSA levels from one time to the next even when no cancer is present (false positive).
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Is there anything else I should know?
Since the DRE can cause a temporary elevation in PSA, the blood is usually collected prior to performing the DRE.
Prostate manipulation by biopsy or resection of the prostate will significantly elevate PSA levels. The blood test should be done before surgery or six weeks after manipulation.
Rigorous physical activity affecting the prostate, such as bicycle riding, may cause a temporary rise in PSA levels. Ejaculation within 24 hours of testing can be associated with elevated PSA levels and should be avoided.
Large doses of some chemotherapeutic drugs, such as cyclophosphamide and methotrexate, may increase or decrease PSA levels.
In some men, PSA may rise temporarily due to other prostate conditions, especially infection. A recent study found that in about half of men with a high PSA, values later return to normal. Some authorities recommend that a high PSA should be repeated, between 6 weeks and 3 months after the high PSA, before taking any further action. Some physicians will prescribe a course of antibiotics if there is evidence that there is infection of the prostate.