The two most commonly used screening methods are the digital rectal exam (DRE) and the prostate-specific antigen (PSA) test.
- Digital rectal examination. During a DRE, a doctor inserts a gloved, lubricated finger into the rectum and feels for 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 test. PSA is a protein in the blood that's produced only by prostate cells. PSA reflects the volume of both cancerous and noncancerous prostate tissue. The higher the PSA level, the more likely prostate cancer is present. PSA test results are reported as nanograms per milliliter (ng/ml). Results below 4.0 ng/ml are usually considered normal. Values above this are regarded as high. The average PSA level increases with age, so values below 4.0 ng/ml for men younger than 60 sometimes warrant a more thorough evaluation. Ask your doctor about acceptable values for your age.
The following tests may be used to make a definitive 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 diagnosis. In most cases, a fine needle is inserted into the prostate gland to withdraw these samples. Local anesthesia is typically used to block pain.
- PSMA PET scan. The PSMA (prostate-specific membrane antigen) PET scan is a new, highly effective imaging technique for detecting prostate cancer cells that have spread to other parts of the body. Patients are injected with a harmless radioactive tracer that attaches to proteins on the surface of prostate cancer cells. The tracer appears bright red on a PET scan, allowing doctors to pinpoint the cancer cells' location and provide the most appropriate treatment. UCSF is one of the first medical centers in the country authorized to offer this test.
- Bone scan. This shows whether prostate cancer has spread to the bones. Low-level radioactive material is injected into the body, and if diseased bone cells are present, they take up the radioactive material. The location of these cells can be seen on the total-body bone scan image and may suggest that metastatic cancer is present, although arthritis and other bone diseases can create the same pattern. A bone scan is generally 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. A CT scan uses a rotating X-ray beam to create a series of pictures of the body from many angles that are put together into a detailed cross-sectional image. This may reveal abnormally enlarged pelvic lymph nodes or spread of the cancer to other internal organs. As with a bone scan, a CT scan may be ordered if there is a markedly elevated PSA, a high Gleason score or evidence of a large tumor.
- Magnetic resonance imaging (MRI). An MRI uses magnetic fields instead of X-rays to create detailed images. These scans are less effective in revealing microscopic cancers, although an MRI using a rectal coil (a device used to improve image quality) is superior to a routine pelvic MRI. A modification that’s still considered experimental, called magnetic resonance spectroscopy imaging (MRSI), may provide more precise information on the cancer’s location in the prostate gland and surrounding area.
- Transrectal ultrasound (TRUS) guided biopsy. To locate the precise area to be biopsied, a small ultrasound probe is placed in the rectum and the sound waves are translated into an image of the prostate on a video screen. Specialists can then distinguish suspicious or abnormal areas of the prostate. An instrument called a biopsy gun, which quickly inserts and then retracts a narrow needle, is used to obtain tissue samples that are sent to the laboratory for examination.
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.