Prostate Cancer: Diagnosis

Approved by the Cancer.Net Editorial Board, 03/2018

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find the cause of a medical problem. Use the menu to see other pages.

Doctors use many tests to find, or diagnose, cancer. They also do tests to learn if cancer has spread to another part of the body from where it started. If this happens, it is called metastasis. For example, imaging tests can show if the cancer has spread. Imaging tests show pictures of the inside of the body. Doctors may also do tests to learn which treatments could work best.

For most types of cancer, a biopsy is the only sure way for the doctor to know whether an area of the body has cancer. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis, but this situation is rare for prostate cancer. For example, a biopsy may not be done when a patient has another medical problem that makes it difficult to do a biopsy, or when a person has a very high PSA level and a bone scan that indicates cancer.

This list describes options for diagnosing this type of cancer. Not all tests listed below are commonly used for every person. Your doctor may consider these factors when choosing a diagnostic test:

  • The type of cancer suspected

  • Your signs and symptoms

  • Your age and medical condition

  • The results of earlier medical tests

Preliminary tests

In addition to a physical examination, the following tests may be used to diagnose prostate cancer:

  • PSA test. As described in the Introduction and Screening sections, PSA is a type of protein released by prostate tissue that is found in higher levels in a man's blood. Levels can be raised when there is abnormal activity in the prostate, including prostate cancer, BPH, or inflammation of the prostate. Doctors can look at features of the PSA value, such as absolute level, change over time (also known as “PSA velocity”), and level in relation to prostate size, to decide if a biopsy is needed.

    • Free PSA test. There is a version of the PSA test that allows the doctor to measure a specific component, called the “free” PSA. Free PSA is found in the bloodstream and is not bound to proteins. A standard PSA test measures total PSA, which includes both PSA that is and is not bound to proteins. The free PSA test measures the ratio of free PSA to total PSA. Knowing this ratio can sometimes help find out if an elevated PSA level is caused by a malignant condition like prostate cancer.
  • DRE. A doctor uses a DRE to find abnormal parts of the prostate by feeling the area using a finger. It is not very precise and not every doctor has expertise in the technique; therefore, DRE does not usually detect early prostate cancer. See the Screening section for more information.

  • Biomarker tests. A biomarker is a substance that is found in the blood, urine, or body tissues of a person with cancer. It is made by the tumor or by the body in response to the cancer. A biomarker may also be called a tumor marker. Biomarker tests for prostate cancer include the 4Kscore, which predicts the chances a man will develop high-risk prostate cancer, and the Prostate Health Index (PHI), which predicts the chances a man will develop prostate cancer.

Confirming the diagnosis

If the PSA or DRE test results are abnormal, then the following tests can help confirm a diagnosis of cancer:

  • PCA3 test. The Prostate CAncer gene 3 (PCA3) assay looks for the PCA3 gene in a man’s urine. Unlike PSA, which can be found in anyone with a prostate, the PCA3 gene is greatly expressed in men with prostate cancer. Using a urine test, a doctor can find out whether this gene is present in the body. This test does not replace PSA. It is used along with a PSA test to help decide if a prostate biopsy is needed.

  • Transrectal ultrasound (TRUS). A doctor inserts a probe into the rectum that takes a picture of the prostate using sound waves that bounce off the prostate. A TRUS is usually done at the same time as a biopsy.

  • Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. To get a tissue sample, a surgeon most often uses TRUS and a biopsy tool to take very small slivers of prostate tissue. Biopsy specimens will be taken from several areas of the prostate. This is done to ensure that a good sample is taken for examination. Most men will have 12 to 14 pieces of tissue removed, and the procedure can take 20 to 30 minutes to complete.

    A person usually can have this procedure done at the hospital or doctor’s office without needing to stay overnight. The patient is given local anesthesia beforehand to numb the area and usually receives antibiotics before the procedure to prevent infection.

    A pathologist then analyzes the sample(s) under a microscope. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

    Ask to review the results of the pathology report with your health care team.

  • MRI fusion biopsy. An MRI fusion biopsy combines an MRI scan (see below) with TRUS. Evaluation with a prostate MRI scan has become a routine procedure in clinical practice. The patient first receives an MRI scan to identify suspicious areas of the prostate that require further evaluation. The patient then has an ultrasound of the prostate. Computer software combines these images to produce a 3D image that helps target the precise area where to perform the biopsy. Although it may not eliminate the need for repeat biopsies, an MRI fusion biopsy can better identify areas that are more likely to be cancerous than other methods. An MRI fusion biopsy should only be performed by someone with expertise in the procedure.

Finding out if the cancer has spread

To find out if cancer has spread outside of the prostate, doctors may perform the imaging tests listed below. Doctors are able to estimate the risk of spread, called metastasis, based on PSA levels, tumor grade, and other factors, but an imaging test can confirm this. Learn more about when these tests are recommended to find out if the cancer has spread.

  • Whole-body bone scan. A bone scan uses a radioactive tracer (Technetium-99) to look at the inside of the bones. The tracer is injected into a patient’s vein. It collects in areas of the bone where metabolic activity has occurred. Healthy bone appears gray to the camera, and areas of injury, such as those caused by cancer, appear dark. It is important to know that structural changes to the bone, such arthritis or bone scars like old fractures, can also be interpreted as abnormal and need to be evaluated by a doctor to make sure they are not cancer.

  • Computed tomography (CT or CAT) scan. A CT scan creates a 3D picture of the inside of the body using x-rays taken from different angles. A computer combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein or given as a liquid to swallow.

  • Positron emission tomography (PET) or PET-CT scan. A PET scan is usually combined with a CT scan (see above), called a PET-CT scan. However, you may hear your doctor refer to this procedure just as a PET scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into the patient’s body. This substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body. For many types of cancer, a PET-CT scan uses fluorodeoxyglucose (FDG) as the substance that is imaged; however, FDG is not a useful substance for imaging in prostate cancer and should not be used.

    Researchers are actively investigating using different substances with PET scans to find prostate cancer. For example, sodium fluoride is absorbed by bones, and its use in a PET scan may improve the chances of finding prostate cancer that has spread to the bone. Other substances being studied include choline acetate, fluciclovine, and prostate specific membrane antigen (PSMA).

  • Magnetic resonance imaging (MRI). An MRI scan uses magnetic fields, not x-rays, to produce detailed images of the body. An MRI can be used to measure the tumor’s size. A special dye called contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a liquid to swallow.

After diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer. This is called staging.

The next section in this guide is Stages and Grades. It explains the system doctors use to describe the extent of the disease and how the cancer cells look under a microscope. You may use the menu to choose a different section to read in this guide.