Further Tests for Prostate Cancer

Free-to-Total PSA (or Free and Bound PSA Ratio, or fPSA)

PSA may be free (not bound to a protein), or bound. Research indicates that if more than 18% of PSA is free, there is less chance of having a high-grade prostate cancer. So, the lower the percentage, the higher the risk. Currently it is not widely used, but knowing this PSA ratio may help avoid further unnecessary tests.

MRI scan

Following referral to a consultant urologist for suspected prostate cancer, you will be recommended for various tests, one of which could now be a non-invasive MRI scan. A Magnetic Resonance Imaging (MRI) scan creates a cross-section of the soft tissues around the selected part of the body by using magnetic fields.

In the past the test was normally done after a biopsy, as a further check to see whether there is any spread outside the prostate. Following advances in technology (both software and hardware), clinicians are now using a multi-parametric MRI (mpMRI) scan of the prostate area before a biopsy is considered, for men with suspected clinically localised prostate cancer (NICE guideline 2019). This has improved considerably the diagnostic capabilities, enabling better detection of clinically significant cancers and reducing unnecessary biopsies and treatment.

Standardisation and consistency of interpreting these contrast enhanced scans has led to a PI-RADS/Likert grading system being adopted and used to evaluate mpMRI of the prostate. Based on a score of 1 to 5, grades 1 and 2 indicate that a significant cancer is unlikely to be present, grades of 3, 4 and 5 indicate an increasingly higher level of probability of cancer. However, the ability to interpret mpMRI depends on the radiologist’s level of experience in this area. Before having an mpMRI scan, some hospitals inject a contrast agent in order to enhance the image, this can occasionally produce side effects that should be explained to you before having the procedure.

Significant tumours can be detected more accurately, therefore allowing any subsequent biopsy to be guided more precisely. If no significant tumour is found on the MRI (PI- RADS/Likert grade 1 & 2) then there may be no need for an immediate biopsy.

Recent advances in MRI scanning techniques and the introduction of advanced software have led to greater accuracy in identifying the position of any tumour and its potential aggressiveness. These are becoming the gold standard, though it will be some time before they come into use in all hospitals.

TRUS Biopsy

Biopsy is a procedure in which a number of small samples of an organ are extracted and examined under a microscope to identify the presence or not of cancer. A Trans-Rectal Ultra-Sound (TRUS) guided biopsy of the prostate is a short procedure that takes place at a hospital as an out-patient. A local anaesthetic is given, but some men can still find the procedure uncomfortable.

TRUS biopsy

 

A lubricated ultrasound probe is first inserted into the back passage in order to provide a ‘map’ of the prostate. The doctor will then pass a fine needle through the rectal wall into the prostate to extract 8–12 samples of tissue cores. These are sent for examination to a pathologist, who will then determine whether any cancerous tissue is present. Antibiotics are given prior to and immediately following the procedure to reduce the risk of infection. There may be a little blood in the urine and/or the back passage for up to three weeks after a biopsy, and blood in the semen for 4–6 weeks. This is not a cause for concern and is normal, but any other symptoms should be referred immediately to your GP or hospital.

As a biopsy takes tiny sample cores from the prostate, it is possible that the needle may miss the cancer. The greater the number of samples taken, the more likelihood of detecting cancer. Greater sampling, however, can lead to increased risk of complications. New techniques (see Fusion Guided Biopsy below) mean that better accuracy is now possible.

 

 

 

 

 

 

 

Template (or Perineal) Biopsy

Because a standard biopsy may miss finding smaller cancers, there is a growing shift towards using a template biopsy, a more precise test which can sample the whole prostate. This can be done when suspicions are high or if a TRUS biopsy result is inconclusive. Many urologists now prefer to recommend this method for patients with high/intermediate risk. The procedure is performed under either a general or local anaesthetic and may require an overnight stay in hospital. A grid will be placed over the perineal area (between the anus and scrotum) through which many more needles can be inserted to take samples (up to 60). As well as being more accurate, a template biopsy is considered safer, as there is less risk of infection from untreatable bacteria compared to a standard TRUS biopsy.

Fusion Guided Biopsy

Recently, new software has been devised that ‘fuses’ the MRI images with the real-time ultrasound probe. The MRI images are overlaid onto the ultrasound image which enables the urologist doing the procedure to pinpoint the suspicious areas with much greater accuracy. It can lead to fewer samples being taken and, for those who may need further biopsies, fewer occasions where a repeat biopsy may be needed. Fusion Guided Biopsy may not be available at all hospitals.

Isotope Bone Scan

This test is to show whether the disease has spread to the bones. A small amount of low-dose radioactive material is injected into the arm about three hours before the scan. The scan takes about 45 minutes, and images of any bones showing the disease will appear on the scan. A bone scan will not usually be done unless the PSA score is greater than 10 and MRI and biopsy samples indicate a high-grade cancer. It is offered when hormone treatment is part of a Watchful Waiting programme for people who are at high risk of developing bone complications. It is painless and quite harmless.

PET Scan

A PET scan (Positron Emission Tomography) is taken to produce a detailed, three-dimensional picture of the inside of the body. Choline PET-CT scans have been shown to be effective for prostate cancer, especially for determining whether there is any spread outside the prostate. Before the scan takes place, a radioactive substance (choline), known as a radiotracer, is passed into your body by injection, by an inhaler, or a small tablet that you swallow. In future, choline PET scans may be replaced by PSMA (Prostate Specific Membrane Antigen) PET scans.

Recent advances in MRI scanning techniques and the introduction
of advanced software has led to greater accuracy in identifying the
position of any tumour and its potential aggressiveness.