The role of a template biopsy in assessing prostate cancer
In order to understand the role of a template biopsy in assessing prostate cancer it is necessary to begin with an explanation of this term. A biopsy is the process by which tiny tissue samples are removed and examined for evidence of cancer. The traditional type of biopsy used in assessing prostate cancer is called a TRUS (transrectal ultrasound imaging) biopsy. In this procedure, the urologist inserts a probe through the rectum and guided by ultrasound imaging, takes about ten to 12 tissue samples from the prostate.
Assessing prostate cancer
When assessing prostate cancer, the use of a template-based biopsy has increased in our practice at BPC during the past decade to the extent that the TRUS method is rarely now used. The term ‘template’ refers to a metal grid which is placed on the perineal. The grid has holes located approximately 5mm apart and needles are inserted through these holes to ensure there is even coverage across the whole of the prostate. A general anaesthetic is used during a template biopsy and MRI is used to map out and guide the process.
Although the TRUS biopsy can be a useful assessment tool, there are disadvantages to this method. Entering the rectum in this way, with the patient under local anaesthetic, means the area furthest from the rectum (the front of the prostate) cannot be fully accessed and sampled. The urologist using TRUS is guided by ultrasound, which provides a lower quality of imaging than other methods such as MRI (Magnetic Resonance Imaging). Equally, a relatively small number of tissue samples are taken. For these reasons, TRUS is associated with a high false negative rate: men who have a negative TRUS biopsy result when cancer is present (in other words, the cancer is not found).
A template based biopsy procedure is better suited to the BPC pathway for most patients in assessing prostate cancer. This is because before a decision to take a biopsy is taken, a number of sensitive assessments will already have been carried out: an enhanced MRI scan and the genetics based PCA3 test as well as the traditional indicators of digital rectal examination and PSA test. This means that once we proceed to biopsy, there is a strong suspicion of prostate cancer and if the biopsy was negative, we would want a high level of confidence in that biopsy result. The weakness of the TRUS biopsy – its high false negative rate – rendering it weak in terms of achieving this confidence.
The template based biopsy procedure is clear in a range of different scenarios: from the patient who is having active monitoring and needs assurance of that care plan through to high risk patients in the planning and all considerations for the treatment they will require.