Consultant Radiologist, The Princess Grace Hospital,
St George's Hospital, London
Dr Patel identified the challenges of diagnosis as cancer of the prostate is difficult to identify visually and increasingly early presentation of patients means that abnormal cell clusters, usually on the edge of the prostate gland, may be relatively small. Biopsy can, therefore, rarely be targeted.
As a result, multiple location biopsies within the gland are generally undertaken - currently, usually eight with recommendations for best practice anticipated at 10-12. The introduction of local anaesthetic has reduced pain levels during biopsies and pre-procedure antibiotics mean that serious complications are rare although there are common minor complications.
Prostate cancer has many unique features.
Firstly, the average volume of disease at diagnosis can be very small. The typical tumour volume may be around 4 ml, which represents a sphere only 2cm in diameter.
Secondly, cancer is almost always presents in an already diseased gland. The gland of the average middle aged men will have undergone some degenerative or other change. Typically, this will be benign prostate hyperplasia, but areas of calcification or inflammation may be present.
Thus, the challenge is to recognise a small volume of tumour in a gland already afflicted by these other disease processes. For both these reasons modern imaging, whether transrectal ultrasound (TRUS) or Magnetic Resonance (MR) Imaging, has a very limited diagnostic accuracy and the standard diagnostic procedure is TRUS guided biopsy.
As the tumour, if present, is most likely to be invisible on TRUS or indistinguishable from adenomas of BPH, multiple biopsies are taken to generally sample the gland. In the past, six biopsies were felt to be sufficiently accurate. However, increasing PSA testing has changed the demographics of prostate cancer at presentation. Younger men are presenting with only mildly elevated PSA and there has been a downward stage migration of disease at presentation.
Multiple biopsies are increasingly used
The modern challenge is to diagnose ever earlier (and smaller) tumours, and novel biopsy strategies have been used. The current standard is to take between 8-12 biopsies and this has been found to boost the accuracy over the traditional sextant pattern by about 20-30%. Furthermore, modern prostate biopsies are also safer and better tolerated.
Eight Biopsies improved the cancer yield from 85% to 97%* in one study . But this is a moving target, and more biopsies may be necessary with downward stage migration.
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Key: The common sites of cancer are shown coloured mauve. The peripheral zone is shown in lightest green (Top = Transverse view; Bottom = Longitudinal view) |
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Transverse illustrations of the Base, Mid portion and Apex of the gland. The trajectories of 8 prostate biopsies are shown |
The use of local anaesthetic means that up to 12 cores can be taken with comfort. Careful randomised trials have confirmed the safety and benefit of local anaesthetic, and almost all men can resume normal day-to-day activity straight away, with only the occasional requirement of simple analgesia.
Although minor bleeding can be expected with all prostate biopsies (e.g. pink tingeing of the urine, mild PR spotting and haematospermia; lasting an average of five days, but occasionally up to 14 days) it does not require any special treatment and eventually clears. Antibiotic prophylaxis is standard and the major complication rate, either septicaemia or significant bleeding, is rare at between 1/100-1/500.
However further refinements in prostate biopsy method are ongoing. With the use of focused therapies there is a need to not only diagnose prostate cancer but to also more precisely map its location. There also some men who have rising PSA or a strong clinical concern of prostate cancer, yet have normal TRUS guided biopsies.
Recent developments at The Princess Grace Hospital address these needs. MR Spectroscopy and transperineal mapped prostate biopsies can study prostate metabolism and provide information about cancer location. MR spectroscopy may help to localise areas of increased metabolic activity which may then be specifically targeted using transperineal template based biopsy.
To summarise the status today:
- Although 8-12 cores for biopsy are now required to ensure a sufficient diagnostic accuracy, with the use of local anaesthetic, it is well tolerated.
- Major complications are rare and the minor side-effects clear without sequelae.
- But the arena of prostate cancer diagnosis is constantly evolving and further changes can be foreseen.
References:
1. Khurshid G, Dundas D, Patel U. Bleeding after transrectal ultrasonography-guided prostate biopsy: a study of 7-day morbidity after a six-, eight- and 12-core biopsy protocol. BJU Int. 2004 Nov;94(7):1014-20.
2. Patel U. TRUS and prostate biopsy: current status.
Prostate Cancer Prostatic Dis. 2004;7(3):208-10.
3. Stamey TA. The era of serum prostate specific antigen as a marker for biopsy of the prostate and detecting prostate cancer is now over in the USA. BJU Int. 2004 Nov;94(7):963-4.
