Q: I am a 58-year-old man. I am seeking advice on which type of prostate biopsy test I should do after having done one earlier.
Three years ago, during a health screening test, I was found to have a prostate specific antigen (PSA) level of 10 micrograms per litre (ug/L).
I underwent a needle biopsy in which 10 tissue samples were taken. The results were normal.
I did further PSA blood-level monitoring at intervals of three months. The PSA levels fluctuated between 5 and 10ug/L.
The doctor then advised me to go for another prostate biopsy.
However, this time, 30 samples will be taken with a method known as template biopsy, which is done under general anaesthesia, he said. This enables a more thorough check and helps to rule out any abnormalities.
My concern is that with such an intrusive method of taking samples, would there be a possibility of some damage occurring to the prostate gland and whether an abnormal condition may turn aggressive?
I understand that there is another non-intrusive method - the magnetic resonance imaging scan - which can supposedly give a more accurate result and is painless.
More information regarding the MRI method will help me to make an informed decision.
A: The prostate specific antigen (PSA) test is not specific to prostate cancer, and levels can be above the usual cut-off point of 4ug/L due to non-cancerous causes, such as a benign enlargement, infection or inflammation of the prostate.
With a PSA level of 5ug/L to 10ug/L, you have an estimated 25 per cent chance of harbouring prostate cancer.
The standard 10-core transrectal ultrasound guided (Trus) biopsy that you underwent has a false negative rate of around 30 per cent.
This means that although your result was normal, there is a 30 per cent chance that this is false, so you may actually have prostate cancer that went undetected.
OPTIONS FOR SECOND TEST
As your PSA levels continue to remain above 4ug/L - the usual threshold which triggers a decision to exclude prostate cancer - you have been offered a second biopsy.
With your previous negative Trus biopsy and continued suspicion of prostate cancer, the options to exclude prostate cancer are to repeat the biopsy either by the Trus method again, or by a transperineal template saturation biopsy.
A transperineal biopsy is done under regional or general anaesthesia in an operating room.
The biopsy needles are inserted through the perineum (the skin between the scrotum and the anus), into the prostate to obtain the tissue sample. An ultrasound probe is placed in the rectum and this guides the placement of the biopsy needles.
The template used is a grid with multiple holes 5mm apart.
In a saturation biopsy, the template grid allows the surgeons to take multiple samples that are evenly spaced out to cover the whole prostate gland.
By increasing the number of samples taken in this manner, the chance of missing an underlying cancer is reduced.
As the transperineal route avoids going through the rectum, there is a near-zero rate of infection as opposed to the approximately 3 per cent rate of infection associated with the Trus biopsy.
With the increasing prevalence of bacteria that are resistant to multiple antibiotics, post-biopsy infections can sometimes be severe and, in rare instances, be life-threatening.
Another advantage of the transperineal route is that it allows sampling of the front parts of the prostate, which can harbour large tumours, but are difficult to reach by the transrectal route.
This allows a more thorough sampling of the prostate.
Potential side effects from a transperineal template saturation biopsy include skin bruising and blood in the urine. These usually go away after a couple of days without the need for any intervention.
Patients may be unable to pass urine after the procedure because of temporary swelling of the prostate, and may require a urinary catheter for a few days until this swelling resolves.
NO PERMANENT DAMAGE
The biopsy needles are very small and are unlikely to cause any permanent damage to the prostate or its surrounding structures.
There is also no evidence that a saturation biopsy will lead to a change in the behaviour of any underlying prostate cancer.
A multi-parametric MRI scan can potentially detect prostate tumours of a significant size.
An increasing amount of data is being reported by several large academic centres that while the MRI cannot detect all prostate cancer cases, the types of cancer that are missed are unlikely to have an impact on a patient's lifespan.
However, more studies are needed to confirm this promising data.
f an MRI scan picks up a tumour in the prostate, a biopsy still needs to be done to obtain proof that it is cancerous before any treatment can be planned.
As a result, while the MRI is a promising tool, it cannot, at this time, replace prostate biopsies as the standard in proving or disproving the presence of clinically significant prostate cancer.
DR LINCOLN TAN, consultant at the department of urology at National University Hospital
This article was first published on Nov 13, 2014.
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