What is PSA?
PSA stands for Prostate Specific Antigen. A PSA test measures the amount of prostate-specific antigen (PSA) in your blood. PSA is a protein which is only produced in the prostate gland, a small gland that sits below a man’s bladder. PSA is mostly found in semen which is produced by the prostate. Small amounts of PSA also circulate in the blood.
The PSA test is used primarily to detect early prostate cancer before it causes symptoms in the body.
What are the causes of elevated PSA?
While high PSA levels can be a sign of prostate cancer, a number of conditions other than prostate cancer can cause PSA levels to rise.
These conditions include:
- BPH: Benign prostatic hyperplasia (Benign enlargement of the prostate)
- Prostate or urine infection
- Prostate inflammation
- Prostate trauma from surgery, biopsy or catheterisation
- Prostate manipulation from prostate examinations, ejaculation or prolonged bike riding
False-positives are common. Only about 1 in 4 men with a positive PSA test turns out to have prostate cancer.
What are the investigations for elevated PSA?
Your doctor may perform further testing to see if the PSA rise is due to prostate cancer or due to other causes. These may include urine tests to assess for infection and inflammation, ultrasound to assess the size of the prostate gland, or a free:total PSA ratio analysis. Your doctor may also choose to repeat the PSA in 3-6 months to see if there is a continued rise in PSA.
If initial test results suggest prostate cancer, your doctor may recommend a procedure to collect a sample of cells from your prostate (prostate biopsy). Prostate biopsy is often done using a thin needle that’s inserted into the prostate to collect tissue. The tissue sample is analysed in a lab to determine whether cancer cells are present.
What is the role of a MRI scan?
The magnetic resonance imaging (MRI) scan uses radio waves and magnetism to build up detailed cross-section pictures of the body. The scan involves lying on an examination table inside a metal cylinder – a large magnet – that is open at both ends.
New evidence suggests that multiparametric magnetic resonance imaging (MRI) has the potential to improve the diagnosis and treatment of prostate cancer.Because the technology is relatively recent, its place in the diagnosis of prostate cancer is still in evolution.
MRI of the prostate can accurately detect clinically significant prostate cancer in 80-90% of cases. MRI scan does not replace prostate biopsy, a biopsy is still required to definitively confirm the prostate cancer. MRI scan may also help improve prostate biopsy accuracy by allowing targeting of the abnormal area by downloading the MRI images on to the corresponding ultrasound images in real time during the biopsy (MRI fusion TRUS biopsy).
MRI of the prostate may also give information about whether the prostate cancer is in close proximity to the nerves that supplies erections which run close to the prostate. This is important for the surgeon to decide if it is safe to peel the nerves off the prostate gland during prostate cancer surgery to help preserve erectile function.
Should I get a PSA test?
There is a lot of conflicting advice about PSA testing. Ultimately, whether you have a PSA test is something you should decide after discussing it with your doctor, considering your risk factors and weighing your personal preferences.
Based on recent data from one of two large randomised screening studies, there was a 21% reduction in the risk of dying from prostate cancer with PSA testing in patients in the 55‐69 year age group after 10 years. Therefore PSA based testing, together with digital rectal examination (DRE), should be offered to men in this age group, after providing information about the risks and benefits of such testing.
Men interested in their prostate health could have a single PSA test and DRE performed at or beyond age 40 to provide an estimate of their prostate cancer risk over the next 10‐20 years based on age‐specific median PSA values, with the frequency of subsequent monitoring being individualised according to the personal circumstances of an individual. Risk of prostate cancer death is very low (<1% at 25 years) for PSA below median PSA.