The prostate specific antigen test (PSA) is the best and most common screening for prostate cancer today, but the results can bring up some important questions. Understanding how the test works and the factors that can influence the results are important topics for a conversation with your doctor, so you can make informed decisions about any possible further interventions.
PSA Test Doesn’t Detect Cancer, It's an Indicator
A man’s PSA level reflects the amount of PSA protein in his blood. The protein is produced by noncancerous cells and cancerous cells in the prostate gland. In addition to cancer, age, infection, trauma, chronic inflammation of the prostate, and certain medications can all influence the PSA level.
Prostate cancer cells typically produce more PSA than benign cells, but it is possible to have an elevated PSA level and not have prostate cancer. It is also possible, but less likely, to have a low PSA and have prostate cancer. The PSA test can be a good indicator for the presence of cancer, but it does not definitively detect cancer.
“It’s difficult to define an absolute cutoff for a normal or abnormal PSA,” said Scott Johnson, MD, a urologic oncologist with the Froedtert & MCW Cancer Network. “As the PSA can be influenced by several factors other than prostate cancer, PSA values really should be interpreted in the context of the individual patient’s age and medical history.”
The PSA test is often done in conjunction with a digital rectal exam (DRE). During the DRE, the doctor will manually examine the prostate by feeling for abnormalities like nodules or hard lumps on the prostate. In some cases, one part of the prostate may feel larger than the other. More men are subsequently diagnosed with prostate cancer based on an elevated PSA than with an abnormal DRE. The DRE is not a perfect test, and results often vary from doctor to doctor.
“There are very few patients in whom we discover prostate cancer with a DRE finding in the face of a low PSA, but it does occasionally happen,” Dr. Johnson said. “Far more cancers will be discovered in men who have an elevated PSA regardless of rectal exam findings.”
If Your Test Results Suggest an Abnormality
If your PSA test or DRE suggests an abnormality, your doctor may recommend a prostate biopsy. The procedure involves obtaining and examining prostate tissue for the presence of cancerous cells. If cancer is detected, treatment may include surgery, radiation therapy, chemotherapy or hormonal therapy. Alternatively, some prostate cancers pose little risk and can be monitored closely rather than treated.
“Prostate cancer can be a slow-growing cancer,” Dr. Johnson said. “It is possible we may find a cancer on the biopsy that does not need to be treated right away, or at all.”
The decision on how to handle the diagnosis will depend not only on biopsy results and PSA, but also on factors such as overall health, family history and age.
One in seven men will be diagnosed with prostate cancer in his lifetime. When it is detected early, prostate cancer is very treatable. Screenings can help detect many cancers early, but the tests and resultant biopsies are a matter of some controversy. Unclear test results could lead to confusion and anxiety — false negatives and false positives are possible. Also, some men may be diagnosed with prostate cancer that may not be dangerous to them because some prostate cancers grow so slowly. These men could still undergo treatment, which can come with side effects (such as erectile dysfunction or urinary incontinence). A prostate cancer specialist, such as a urologic oncologist, can help determine the best course of action.
“It is important to understand the potential outcomes from having a PSA test,” Dr. Johnson said. “If treatment for prostate cancer is not something a man would consider, we should never go looking for it.”
Research is underway to determine if early detection tests, such as the PSA test, will lower the risk of death from prostate cancer. So far, according to the American Cancer Society (ACS), results have been inconclusive.
Given the prostate cancer incidence and mortality rates in Wisconsin and the opportunity to improve survival through early detection, the Froedtert & MCW health network recommends care in keeping with the American Cancer Society prostate screening guidelines, which state men should have an informed discussion with their doctor about prostate cancer screening at:
- Age 50: Men who are at average risk of prostate cancer and are expected to live at least 10 more years.
- Age 45: Men at high risk of developing prostate cancer. This includes African-Americans and men who have a first-degree relative (father, brother, or son) diagnosed with prostate cancer at an early age (younger than age 65).
- Age 40: Men at even higher risk (those with more than one first-degree relative who had prostate cancer at an early age).