Laboratory testing may be used to screen asymptomatic and symptomatic men for prostate cancer, rule out other diseases and conditions that may be causing or worsening a person's symptoms, monitor the effectiveness of treatment for cancer, and monitor for recurrence.
Testing may include:
- PSA (total prostate specific antigen) – to help screen for and monitor prostate cancer. PSA is a good but not perfect tool. Some organizations, such as the U.S. Preventive Services Task Force, feel that the harms associated with over-diagnosis and over-treatment outweigh the potential benefits and advise against using PSA to screen for prostate cancer in healthy men of any age. The American Cancer Society, American Urological Association, and American College of Physicians recommend that men discuss the advantages and disadvantages of PSA-based screening for prostate cancer with their healthcare provider before making an informed decision about whether to be screened or not. (See Screening Tests for Adults (30-49): Prostate cancer and Screening Tests for Adults (50 and Up): Prostate cancer for details on screening recommendations.)
Increased levels of total PSA have been associated with an increased risk of prostate cancer but are also found with BPH, prostatitis, infection, and a variety of other temporary conditions. When evaluating the results, the healthcare provider must consider both the level of PSA in the blood and the volume of the man's prostate. (See the PSA test page for discussion of variations of the PSA test.)
- The digital rectal exam (DRE) is a physical examination. To perform the DRE, a health practitioner inserts a gloved, lubricated finger into the rectum and feels the prostate gland with his finger to detect abnormalities. Photo source: National Cancer Institute, Alan Hoofring
- Free PSA – PSA exists in two main forms in the blood: complexed (cPSA, bound to other proteins) and free (not bound). The free PSA test may be used to help to determine whether a biopsy should be done when the total PSA is only slightly elevated. Men with BPH tend to have higher levels of free PSA and men with prostate cancer tend to have lower amounts of free PSA. A relatively low level of free PSA increases the chances that a cancer is present, even if the total PSA is not significantly elevated.
Similar to free PSA, some other tests have been developed to aid some men and their healthcare providers in decisions about the whether to undergo biopsy. Biopsies used in follow up to positive PSA results can cause discomfort, anxiety, and sometimes complications. These tests are relatively new and not yet widely available:
- [-2] proPSA – this test looks for a precursor of PSA, which may be produced by prostate cancer cells at a higher rate than benign prostate cells. The percentage of [-2] proPSA relative to the total PSA level has been used, like the % free PSA, to help decide whether a biopsy is indicated.
- PCA3 – PCA3 is a protein produced only in the prostate gland. The test measures the urine level of PCA3 messenger RNA (m-RNA), a signal from genes that tells the prostate to produce the PCA3 protein. Increased amounts of the m-RNA (over-expressed) are produced by 95% of prostate cancer cells, so an elevated level may help to indicate that a prostate cancer is present.
- TMPRSS2-ERG gene fusion – this test is also a urine-based assay. It detects mRNA that is the result of a gene rearrangement. The gene rearrangement is over-expressed in more than 50% of prostate cancers, so an elevated level may help to indicate that a prostate cancer is present.
These tests do not provide a definitive answer as to whether a man has a prostate cancer or not. Rather, they are intended to help predict whether a biopsy would be useful in helping to establish a diagnosis.
The gold standard for diagnosing prostate cancer is the prostate biopsy, collecting small samples of prostate tissue and identifying abnormal cells under the microscope. If cancer is found, the health practitioner will use the sample and imaging tests, such as an ultrasound, to determine the cancer's stage (how far it has spread into the body) and grade (how abnormal the cells appear). The more abnormal the tumor cells are, the more likely it is that the cancer will be aggressive.
Sometimes other tests may be done to rule out other conditions that cause similar symptoms:
- Urinalysis – to screen for kidney disorders and urinary tract infection (UTI)
- Urine culture – to help diagnose a UTI
- Blood urea nitrogen (BUN) and Creatinine – blood tests to evaluate kidney function
Non-laboratory tests may include:
- Ultrasound – a transrectal ultrasound (TRUS) may be used to help measure the size of the prostate and to help guide needle placement during a prostate biopsy
- CT (computed tomography) – to help evaluate the extent of the cancer
- MRI (magnetic resonance imaging) – to help evaluate the extent of the cancer
- Radionuclide bone scintigraphy – occasionally used to detect cancer that has spread to bone
- PET (positronic emission tomography) – occasionally used to help stage metastatic cancer (cancer that has spread beyond the prostate)