Prostate Specific Antigen (cont.)
Kevin C. Zorn, MD, FRCSC, FACS
Dr. Kevin Zorn is a dual-board-certified (US and Canada), minimally-invasive uro-oncology, fellowship trained urologist at the University of Chicago. His main focus of clinical and scientific interest is in the surgical treatment of renal and prostate cancer. He is also an expert in performing surgery with the DaVinci Surgical Robotic System to manage localized prostate cancer and small renal masses. Dr. Zorn studied medicine and urology at McGill University in MontrĂ©al.
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
In this Article
- Prostate specific antigen (PSA) test facts
- What is prostate specific antigen (PSA)?
- How is PSA test measured?
- What causes PSA elevation in the blood?
- What are normal results for the PSA test?
- What are age-specific reference ranges for serum PSA?
- How is PSA used for early detection of prostate cancer?
- What is the free PSA test?
- What is free/total PSA ratio?
- What is PSA velocity and PSA doubling time?
- How is PSA testing used for pretreatment staging of prostate cancer?
- How is PSA testing used in the management of prostate cancer after treatment?
- What are the limitations of the PSA test?
- What is digital rectal examination (DRE)?
- What is the PSA screening controversy?
- How should the PSA test be used for the early detection of prostate cancer?
- What is PCA3?
- What is the 4K biomarker?
What are age-specific reference ranges for serum PSA?
The use of age-specific PSA ranges for the detection of prostate cancer is helpful to avoid unnecessary investigations in older men with larger prostate glands. Not all studies have agreed that this is better than simply using a level of 4.0 ng/mL as the highest normal value. Nevertheless, due to the age-related growth of the prostate, the concept of adjusting the cutoff values based on age has helped reduce unnecessary prostate biopsies in older men to improve early prostate cancer detection. Below are the suggested age-adjusted values based on age and race.
|Age Range (Years)||Asian Americans||African Americans||Caucasians|
|40 to 49||0 to 2.0 ng/mL||0 to 2.0 ng/mL||0 to 2.5 ng/mL|
|50 to 59||0 to 3.0 ng/mL||0 to 4.0 ng/mL||0 to 3.5 ng/mL|
|60 to 69||0 to 4.0 ng/mL||0 to 4.5 ng/mL||0 to 4.5 ng/mL|
|70 to 79||0 to 5.0 ng/mL||0 to 5.5 ng/mL||0 to 6.5 ng/mL|
How is PSA used for early detection of prostate cancer?
Clinically localized prostate cancer generally does not usually cause any symptoms. In general, most men with organ-confined (early, localized) prostate cancers have diagnostic PSA values from less than 10 up to 20 ng/mL. Once PSA values are greater than 20 ng/mL, the risk for metastatic (distant spread) disease grows exponentially. Men with early prostate cancer usually feel perfectly well and have no urinary symptoms. As mentioned previously, the gold standard of prostate biopsy to detect prostate cancer is commonly initiated by an abnormal prostate digital rectal examination and/or an abnormal PSA value. It is for this reason that early detection tests have been developed in order to detect prostate cancer while it remains clinically silent and confined to the prostate. Hence, in clinical practice, tests used to detect prostate cancer include serum PSA level, digital rectal examination (DRE), and transrectal ultrasonography (TRUS).
More recently, other novel biomarkers and tests (PCA3, 4K as well as prostate MRI imaging) have emerged as additional adjuncts to patient counseling. Unfortunately, none can confirm the presence of prostate cancer.
Although not perfectly specific as a biomarker, the level of PSA has been demonstrated to be an independent variable to predict the presence of prostate cancer. In fact, the higher the level, the more likely prostate cancer is present. An abnormal result will usually require additional testing. However, definitive diagnosis of prostate cancer depends on the presence of cancer cells obtained either from prostate biopsy or surgical specimens.
In general, PSA levels greater than 4 ng/mL are usually considered suspicious. As levels increase above 10.0 ng/mL, the probability of cancer increases dramatically. However, not all men with prostate cancer have elevated PSA levels. It is known that a small but significant number of people with prostate cancer can present with a PSA level of less than 4.0 ng/mL. This is why doctors may use lower thresholds to decide when to do a biopsy.
For an average man over the age of 50 with a normal digital rectal exam, the average probability of having prostate cancer detectable by prostate biopsy according to his PSA level is as follows:
|PSA Level (ng/mL)||0 to 2.0||2.0 to 4.0||4.0 to 10.0||greater than 10.0|
|Prostate Cancer on Biopsy (%)||10%||25%||17% to 32%||43% to 65%|
Since the likelihood of having prostate cancer increases proportionately with PSA level, there is no threshold below which a man can be reassured that prostate cancer is not present.
In order to improve the specificity of the PSA test in the early detection of prostate cancer, several modifications of the serum PSA value have been described including the ratio of free/total PSA and the measurement of PSA change over time.
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