The two most commonly used methods for screening are the digital rectal exam and the prostate-specific antigen (PSA) test.
- Digital Rectal Examination (DRE) During a digital rectal exam, a doctor inserts a gloved, lubricated finger into the rectum to feel for any irregular or abnormally firm areas in the prostate. Some, though not all, prostate cancers can be detected this way. The DRE also can be used to monitor the progress of treatment.
- Prostate-Specific Antigen (PSA) Test Prostate specific antigen (PSA) is a protein in the blood that is produced only by prostate cells. PSA reflects the volume of both benign and malignant prostate tissue. The higher the PSA level, the more likely it is that prostate cancer is present. PSA test results are reported as nanograms per milliliter (ng/ml). Results less than 4.0 ng/ml usually are considered normal. Values over this are regarded as high. The average PSA level increases with age, so some values below 4.0 ng/ml for men younger than 60 should warrant a more thorough evaluation. Ask your doctor for acceptable values for your age.
The following tests may be used to make a definite diagnosis of prostate cancer:
- Biopsy A biopsy is performed to obtain samples of prostate tissue, which are then examined by a pathologist, to make a formal diagnosis of prostate cancer. In most cases, a fine needle is inserted into the prostate to withdraw small samples of tissue. Local anesthesia is typically used.
- Bone Scan This test shows if cancer has spread from the prostate to the bones. Low level radioactive material is injected into the body. If diseased bone cells are present, they will take up the radioactive material. This allows the location of diseased bone to be seen on the total body bone scan image. These areas may suggest that metastatic cancer is present, although arthritis and other bone diseases can create the same pattern. Usually, a bone scan is ordered only if there are signs of aggressive disease such as a markedly elevated PSA level, a high Gleason score — a prostate cancer grading system — or a large tumor.
- Computed Tomography (CT) Scan This test uses a rotating X-ray beam to create a series of pictures of the body from many angles that can be put together into a detailed cross-sectional image. This can help reveal abnormally enlarged pelvic lymph nodes, or spread of the cancer to other internal organs. A CT scan usually is ordered if there is a markedly elevated PSA, a high Gleason score — a prostate cancer grading system — or evidence of a large tumor.
- Magnetic Resonance Imaging (MRI) Similar to a CT scan, this test uses magnetic fields instead of X-rays to create detailed images. These scans are less effective in revealing microscopic-sized cancers, although an MRI using a rectal coil is superior to a routine pelvic MRI. A modification of the MRI that is still considered experimental, called magnetic resonance spectroscopy imaging (MRSI), may provide more precise information on where the cancer is located in the prostate gland and the surrounding area.
- Transrectal Ultrasound (TRUS) Guided Biopsy This test uses sound waves produced by a small probe placed in the rectum to create an image of the prostate on a video screen. The echoes from the waves are translated by a computer into a picture that can show the location of suspicious or abnormal areas of the prostate. An instrument called a biopsy gun quickly inserts and removes a narrow needle, obtaining small cores of tissue that are sent to the laboratory for examination. The entire prostate should be sampled since cancer may not be seen with the TRUS.
UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.