How is prostate cancer diagnosed?

Prostate specific antigen (PSA) is a protein made by both normal prostate cells and cancerous prostate cells. PSA is found in the blood and can be measured with a blood test. The test results will show the level of PSA in your blood as nanograms of PSA per millilitre (ng/mL) of blood.

There is not one normal PSA level for everyone. If your PSA level is above 3 ng/mL (called the  threshold), this may be a sign of prostate cancer. Younger people or people with a family history of prostate cancer may have a lower threshold. PSA levels can vary from day to day. If your PSA is higher than expected, your GP will usually repeat the test to help work out your risk of prostate cancer.

Your PSA level can be raised even when you don’t have cancer. Other common causes of raised PSA levels include benign prostate hyperplasia, recent sexual activity, an infection in the prostate, or a recent digital rectal examination. Some people with prostate cancer have normal  PSA levels for their age range.

Free PSA or free-to-total test

Your doctor may also suggest that you have a free PSA test. This test measures the ratio of free  PSA to total PSA in your blood. Free PSA is PSA that is not attached to other blood proteins. This test may be suggested if your PSA level is between 4–10 ng/mL and your doctor is not sure whether you need a biopsy. A low free-to-total PSA ratio may be a sign of prostate cancer.

To do a digital rectal examination (DRE), the urologist places a finger into your rectum to feel the back of the prostate. They’ll wear gloves and put gel on their finger to make the  examination more comfortable.

You may have further tests if the specialist feels a hardened area or an odd shape. These changes  do not always mean you have prostate cancer. Having a normal DRE also does not rule out  prostate cancer, as the finger can’t reach all of the prostate and the examination is unlikely to pick up a small cancer.

A DRE is no longer recommended as a routine test for GPs to do, but a urologist will use it to help assess the prostate and decide if you need further tests.

An MRI (magnetic resonance imaging) scan uses a powerful magnet and radio waves to build up detailed pictures of the inside of the body. A specialised type of MRI called mpMRI (multiparametric magnetic resonance imaging) is used to help find prostate cancer. It combines the results of three MRI images to provide a more detailed image.

Your doctor may suggest you have an MRI to help work out if a biopsy is needed or to guide the biopsy needle to a specific area of the prostate. This scan can also be used to show if the cancer has spread from the prostate to nearby areas.

Before the scan, let your medical team know if you have a pacemaker or any other metallic object in your body. If you do, you may not be able to have an MRI scan as the magnet can interfere with some pacemakers. Newer pacemakers are often MRI-compatible.

Having an MRI

Sometimes a dye (known as contrast) is injected into a vein before the scan to help make the  pictures clearer. You will lie on an examination table that slides into the scanner, a large metal cylinder open at both ends. The person doing the scan will place you in a position that will allow you to stay still and limit movement during the scan.

The scanner makes loud repetitive sounds during the scan. The scan is painless but the noisy and narrow MRI machine makes some people feel anxious or claustrophobic. If you think you could become distressed, mention it beforehand to your medical team.

You may be given a mild sedative to help you relax, or you might be able to bring someone into the room with you for support. You will usually be offered earplugs or headphones to listen to music.  The MRI scan may take around 30 minutes.

Medicare rebates for MRI scans to detect prostate cancer are only available if the MRI is ordered by a specialist and you meet certain conditions. You may have to also pay a gap fee. There is currently no Medicare rebate for PET scans for prostate cancer. Ask your doctor or imaging centre what you will have to pay.

Depending on the results of the MRI scan, your urologist may recommend you have a biopsy to remove some samples of tissue from the prostate. They will explain the risks and benefits of having a prostate biopsy and give you time to decide if you want to have one.

There are two main ways to perform a prostate biopsy. In a transperineal (TPUS) biopsy, the needle is inserted through the skin between the anus and the scrotum. In a transrectal (TRUS) biopsy, the needle is inserted through the rectum. During either procedure, the doctor may take a number of samples from different areas of the prostate and also remove a sample from any suspicious areas seen on the MRI.

A TPUS biopsy is normally done under general anaesthetic. The specialist passes a small ultrasound probe into your rectum. An image of the prostate appears on a screen and helps guide the needle into place.

Depending on the type of biopsy you have, after the procedure you may see a small amount of  blood in your urine or bowel motions for a few days, and blood in your semen for a couple of months. After a TPUS biopsy, the risk of infection is extremely low. There is a greater risk of infection with a TRUS biopsy, but the risk is still low.

The samples are sent to a laboratory, where a specialist doctor called a pathologist looks for cancer cells in the tissue. Waiting for the results can be a stressful time. It may help to call Cancer Council 13 11 20.

If the biopsy results show prostate cancer, other tests may be done to work out whether the cancer has spread. 

Bone scan

This scan can show if prostate cancer has spread to your bones. Before the scan, a tiny amount of radioactive dye is injected into a vein. The dye collects in areas of abnormal bone growth. You will need to wait for a few hours while the substance moves through your bloodstream to your bones. Your body will be scanned with a machine that detects the dye. A larger amount of dye will usually show up in any areas of bone with cancer cells. The scan is painless and the radioactive substance passes from your body in a few hours.

CT scan

A CT (computerised tomography) scan uses x-rays to create detailed pictures of the inside of the body. A CT scan of the abdomen can show whether cancer has spread to lymph nodes in that area. A dye is injected into a vein to help make the scan pictures clearer. You will lie still on a table that moves slowly through the CT scanner, which is large and round like a doughnut. The scan itself takes a few minutes and is painless, but the preparation takes 10–30 minutes.

PET–CT scan

A PET (positron emission tomography) scan combined with a CT scan is a specialised imaging test. A PET–CT scan may help detect cancer that has spread or come back. For prostate cancer, the scan usually looks for a substance produced by prostate cancer cells called prostate specific membrane antigen (PSMA). Before the scan you will be injected with a small amount of a radioactive solution that makes PSMA show up on the scan. The cost of this scan is not yet covered by Medicare.