The earlier a cancer is diagnosed the better. That’s because when it isn’t too large and hasn’t spread there are generally more treatment options available.
One way in which we can help diagnose cancers earlier is through screening programmes. This is when people without cancer symptoms are tested for the disease.
Currently, there are three screening programmes in the UK, for breast, bowel and cervical cancer. These programmes help to save thousands of lives each year. England is also in the process of introducing a new targeted lung cancer screening programme for people at high risk of the disease.
But why isn’t there a screening programme for prostate cancer? Here, we take a look at some of the latest research into PSA testing to find out.
What is the PSA test?
The PSA test measures the amount of prostate specific antigen (PSA) in the blood. PSA is a protein made by both normal and cancerous prostate cells.
Its normal for all men to have some PSA in their blood. High levels of PSA can be a sign of prostate cancer, but PSA levels can also be raised because of other conditions, such as a urine infection.
It’s important to note that a prostate cancer diagnosis is not made on PSA level alone. Instead, PSA testing can be used to help a doctor to decide whether to undertake further tests, such as an MRI scan or biopsy.
Why is the PSA test not used for prostate screening?
You may have heard people suggesting the PSA test be used to screen people for prostate cancer, or you may even know someone who had the PSA test when they had no symptoms.
But currently the UK National Screening Committee (NSC) – the independent organisation that reviews the evidence for screening programmes – do not recommend PSA testing for prostate screening because the harms do not outweigh the benefits.
That is because the PSA test is not reliable or accurate enough at finding prostate cancer. This means that it can miss some cancers (false negative) or can suggest someone has cancer when they don’t (false positive). It can also lead to overdiagnosis.
The problem of overdiagnosis
Not all prostate cancers are the same. Some grow fast and spread quickly, while others grow slowly. Some of these cancers grow so slowly (or not at all) that if they went undetected they wouldn’t cause any problems and the person wouldn’t be harmed by their cancer if it was left untreated.
When these harmless cancers are found, they are said to be ‘overdiagnosed’.
Because it’s impossible to tell the potentially harmful prostate cancers from the harmless ones, men who are diagnosed with prostate cancer are usually offered treatment. So in some cases, men are unnecessarily treated for prostate cancer that would never have harmed them.
These treatments can have a serious impact on people’s lives, including the possibility of infection following a biopsy and erectile dysfunction and bladder problems following treatment.
What does the latest research show?
The CAP trial is the largest ever study into prostate cancer screening to date. It included over 400,000 men aged 50-69 spanning almost 600 GP practices across the UK.
Recently, the 15-year follow up of the study was published in the American Medical Association (JAMA). The study found that a single invitation to a PSA blood test for men without symptoms had little impact on reducing prostate cancer deaths, reducing mortality by less than 1 man for every 1,000 invited for screening.
The results of the trial also showed that an estimated 1 in 6 cancers found by the single PSA screening were overdiagnosed which may have led to unnecessary and invasive treatment.
There have been improvements in diagnosing and treating the disease in the years since this trial began, including the introduction of MRI before biopsy. These changes may help to prevent some harms associated with PSA testing, but more research is needed on ways to find aggressive cancers that need to be treated.
