What is a PSA test?
A PSA test measures the level of prostate specific antigen (PSA) in the blood. It can help to diagnose prostate disease.
Prostate specific antigen is a protein made in the prostate gland. Low levels of PSA are normally present in the blood but as a man gets older, the prostate often grows and the level of PSA gets higher.
PSA is not a test specifically for cancer. A raised PSA level in the blood just means something is happening in the prostate which, in many instances, is not due to cancer.
The causes of raised PSA levels include the benign (non-cancerous) growth of the prostate that happens with ageing (benign prostatic enlargement); inflammation or infection of the prostate (prostatitis); and prostate cancer.
Is a PSA test worth having if I have no symptoms?
Although there are still questions about the value of PSA as a test for prostate cancer, it is the standard first line test to screen for prostate cancer.
One of the problems with using the PSA test to detect prostate cancer is that there are high numbers of false positive and sometimes false negative results.
A false positive result is when PSA levels are raised but there is no prostate cancer found on biopsy. A false negative result is when PSA levels are low or within the normal range, but prostate cancer is actually present.
In the early stages, prostate cancers usually do not show any symptoms. Cancer can grow in the prostate and not affect urine flow until it is at a late stage. A PSA test can be a sign of prostate problems before symptoms have started.
How good is the PSA test for finding prostate cancer?
About one in three men with a PSA level between 4 and 10 ng/ml will have prostate cancer, although this proportion varies with the population tested.
Studies have shown that there is still a small risk of prostate cancer even if blood PSA levels are normal for age (a false negative result). Therefore, even a normal blood PSA level does not mean that there is definitely no prostate cancer present.
When should I start testing my PSA?
PSA testing should begin at age 40 in order to provide a baseline estimate of the risk of finding prostate cancer at an older age.
Why is biopsy necessary to diagnose prostate cancer?
The only way to confirm whether prostate cancer is present is by prostate biopsy. The biopsy, to remove small tissue samples from the prostate, is usually done by a urological surgeon. The samples are sent to a pathologist to be looked at under a microscope to see if cancer is present, and if so, whether it looks aggressive or not.
A transrectal or transperineal ultrasound-guided biopsy of the prostate gland uses ultrasound, with a probe placed in the rectum (back passage), to outline the prostate and guide the doctor in where to place the biopsy needles for collecting the tissue samples.
Transrectal or transperineal biopsies can be unpleasant and at least half of men have minor symptoms for a day or two afterwards. With a transrectal biopsy, there is also a small risk of serious infection (septicaemia) even when ‘covering’ antibiotics are used. The risk of infection with transperineal biopsy is close to zero; however, this method of biopsy usually needs a general anaesthetic.
The way that we have managed and evaluated or abnormal PSA or prostatic specific antigen test has changed significantly over the last few years. The PSA test is a blood test that essentially assesses the “health” of the prostate.
Part of the issue with the test is that although it is specific for the prostate, the PSA test is not specific for one prostatic condition. There are three common conditions that can cause an elevation in this blood test. These include enlargement of the prostate, or BPH, which increases in frequency with age, inflammation of the prostate (prostatitis) and prostate cancer itself. Previously, abnormalities in the PSA value would be evaluated with a transrectal ultrasound guided (TRUS) prostate biopsy.
The main issue with this technique is that it involves the passage of needles through the rectal wall which in turn carries with it a ‘not insignificant’ risk of infection or sepsis after the biopsy. It is infection from the biopsy which is one of the main deterrents to undergoing PSA testing itself. Moving forward from this point a transperineal route has been more commonly adopted due to a reduction in the incidence of infection, and is certainly the standard way that we at the prostate clinic evaluate abnormal PSAs. In fact, over the last four years since adopting this transperineal or transcutaneous route for biopsying the prostate, we have yet to experience a single case of infection.
More recently, multiparametric MRI has come on the scene, and this facilitates obtaining an image of anatomical details within the prostate so that any subsequent biopsy can be performed in a more targeted fashion. The aim ultimately is to be more discerning about who undergoes a biopsy and when required, to perform this biopsy in a more specific targeted fashion.
It should be mentioned that although a great advancement, an MRI itself is not 100% full proof and there are certain situations where an MRI will not detect significant prostate cancer. It is an excellent tool detecting discreet solitary lesions within the gland but is less useful for detecting less focal more diffuse lesions. It is for these reasons that a combination of both MRI and transperineal prostate biopsy are tailored according to the specific clinical scenario. For more information about the details of a Multiparametric MRI, please refer to our previous blog from our colleagues at South Coast Radiology from the 21st March 2014.
Resources: www.andrologyaustralia.org
