taken from Small Gland, Big Problem 4th Edition
by Professor Roger Kirby, Health Press 2011
PSA measurement and digital rectal examination are both important for staging, but you will almost certainly have to undergo some further tests.
Ultrasound may be used to assess the size and texture of the prostate; the specific technique is called transrectal ultrasonography (or TRUS for short). A lubricated probe is inserted into the rectum, where it passes high-frequency sound waves through the prostate. Computer analysis of the echoes, which vary according to the density of the tissues the waves are passing through, produces an image of the prostate that can then be seen on a screen. Ultrasound is a relatively simple and safe procedure that is not too uncomfortable, but without a biopsy it cannot be used to tell definitively whether or not cancer is present.
Ultrasound-guided biopsy is used to obtain tiny samples of tissue from your prostate that can then be sent to the pathology laboratory for analysis under a microscope. The pathologist can check whether cancer is present and, if it is, grade it. You will probably be recommended for biopsy, an outpatient procedure, on the basis of your PSA level.
Using ultrasound for guidance, a probe with a fine needle attachment is inserted into the back passage until it reaches the prostate (shown in the diagram on the next page). The test is not too painful, but you may feel a sharp needle prick, even if a local anaesthetic has been used, as 8–12 or sometimes more tissue samples are taken. The results should usually be available within a few days.
A variation on the standard biopsy is the template transperineal biopsy. This involves inserting a fine needle through the skin between the scrotum and the anus many times in order to obtain tissue samples from the prostate for testing. The procedure is usually carried out with a light general anaesthestic, which enables many more samples to be taken than would be tolerated using the standard method. It also reduces the rate of infection, though it may result in some difficulty passing urine for several days after the procedure.
It’s important to appreciate, though, that biopsies of the prostate are only tiny samples of the whole gland, so small cancers may sometimes be missed. If the PSA continues to rise in spite of a negative biopsy result, a further set of biopsies may be required. Several studies have shown that prostate cancer is unlikely to be present in a man who has had three consecutive negative biopsies; BPH is likely to have triggered the PSA rise in this case.
You will usually be given antibiotics (tablets or an injection) for 24 hours or immediately before the procedure, and you will be told to continue taking the prescribed antibiotic tablets for several days afterwards. For several weeks after the procedure, you may notice blood in your urine, semen and/or bowel motions. This is quite normal, but if you have any worries, consult your doctor. Urinary infections and septicaemia occur in 2–5% of men as a consequence of the biopsy – if you feel a burning sensation on urination, notice that your urine is cloudy and/or smelly, find that you have to urinate more frequently than normal and/or you develop a temperature, have shaking attacks and feel generally unwell, you must contact your doctor. He will probably prescribe more antibiotics or even admit you to hospital for antibiotic treatment using an intravenous drip. E. coli bacteria are usually responsible for these problems.
Patients often ask whether having a biopsy will cause the cancer to spread. The ability to spread (to metastasize) to other parts of the body, such as the bones, depends on the characteristics of the cancer cells themselves and tends to occur quite late in the disease.
Bone scans are a means of checking whether the cancer has spread (metastasized) around the body to the bones. Three hours before you have the scan, a mixture containing radioactive particles (radionuclides) will be injected into your arm. The particles then spread around your body; their pattern, which shows up on the scanner, can reveal ‘hot spots’, which are dark areas of abnormal blood flow – a sign that cancer may be present. ‘Hot spots’ can also be the result of other diseases, such as arthritis in the joints and spine, so further testing may be necessary to clarify the cause of an abnormal scan. Do not be concerned about the use of radiation here – the amount is so low that the risk to your health is negligible.
MRI, or magnetic resonance imaging, is a technique whereby a strong magnetic field and radio signals are used to examine sequential cross-sections of the body. The images that result are highly detailed – the radiologist and urologist can use them to assess the extent of the cancer in the prostate and to check whether any secondary tumours have formed in other regions. The procedure is completely painless, but some people find being in the scanner rather claustrophobic. The results should be available within a few days. If you have recently had a biopsy, the MRI will often be delayed for 4–6 weeks to allow the biopsy reaction to settle.
If you have any metal implants, such as a pacemaker or coronary artery stents, it is usually not possible to perform an MRI scan, so a CT scan will probably be arranged as an alternative.
CT, or computed tomography, is similar to MRI in that the technique produces images of sequential slices through the body, but it uses X-rays to build up the images. CT scanning is not as accurate as MRI in terms of looking at the prostate, but is much less claustrophobic. Occasionally, CT scanning is used to guide biopsy needles to obtain tissue samples from enlarged lymph nodes or other soft tissues. It is also used when planning radiotherapy to target the prostate and the cancer within it.
Why scans are not always necessary
Although you might think that every man who has been diagnosed with prostate cancer requires scanning, in fact, in men with a PSA below 10 ng/mL, the chances of a positive scan are so low that they are often not recommended. Many patients feel reassured to know that their scans are clear, but remember that bone scans can give false-positive results and MRI scans can also sometimes be misleading as they cannot reliably detect microscopic spread outside the prostate.
Although the tests described above seem very ‘high tech’ and sophisticated, unfortunately they do not always give a very precise answer to the question ‘has the cancer spread beyond the prostate?’ In fact the so-called ‘Partin’s tables’, which compare the findings of the rectal examination, the PSA level and the Gleason score, are still often the best way of estimating the risk of spread beyond the prostate capsule.
These tables were developed by Dr Alan Partin, now the Professor of Urology at the renowned Johns Hopkins University Hospital, Baltimore, USA. He has shown that the smaller the cancer feels on rectal examination, and the lower the PSA level and Gleason score, the greater the likelihood that the cancer can be completely removed by surgery. These tables can therefore be useful in helping the doctor, patient and family decide together on the best treatment option.