If prostate cancer is suspected by an abnormal PSA test or an abnormal feeling prostate on examination, a biopsy is required to make the diagnosis. With a biopsy, multiple small samples of prostate tissue are extracted with a needle under ultrasound guidance, which are then sent to a pathologist to be examined under a microscope to look for cancer cells.
There are currently two methods for performing a prostate biopsy, both have advantages and disadvantages. A transrectal ultrasound biopsy (TRUS) may be performed under local anaesthesia and involves 12 biopsies taken with a needle through the rectum to access the prostate. This is quick and simple to do, but some prostate cancers may be missed on the first biopsy as this method does not provide good access to the anterior (front) part of the prostate which is away from the rectum. The risk of a serious infection is higher with this method (1-2%) as the needle is passing through a contaminated area before reaching the prostate.
Transperineal Prostate Mapping is slightly more invasive and is performed under a general or spinal anaesthetic. The biopsy needle is passed through the perineum (the skin between the scrotum and anus) to reach the prostate. A special biopsy grid is used in conjunction with an ultrasound to provide a grid referenced “map” of the prostate. Between 24 and 38 biopsies are taken, tailored to the size of your prostate. This allows for a more accurate and reliable test in many cases and the chances of requiring a second biopsy are less. The risk of serious infection in lower (<0.5%) as the perineal skin may be cleaned with antiseptic before the biopsies are taken. The downsides to this method are that it cannot be done under local anaesthesia and the risk of difficulty urinating afterwards is higher as the increased number of biopsies taken increase the trauma and swelling of the prostate after the procedure.
Advantages of Transperineal Prostate Mapping Biopsy
- Increased prostate coverage
- Increased accuracy
- Less chance of requiring a second biopsy
- Less risk of serious infection (<0.5%)
Disadvantages of Transperineal Prostate Mapping Biopsy
- Cannot be done under local anaesthesia
- More invasive
- Greater risk of difficulty urinating after the procedure
Common side effects of either prostate biopsy technique
- Blood in the urine (2-3 days)
- Blood in the faeces (2-3 days)
- Discolouration of the ejaculate (up to 6 weeks)
- Difficulty with urination (up to 2 weeks)
In the following video published online by the British Journal of Urology International (BJUI), Dr James Symons discusses the outcome of the worlds larges published series of Transperineal Prostate Mapping Biopsy. This is part of the excellent work by Professor Phillip Stricker from St Vincents hospital, Sydney. Professor Stricker is a world leader in this technique.