The PSA screening debate

For the last 15 years, the PSA test has been considered the first line of defence against prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body., both for diagnosisThe process of determining which condition a patient may have. of men with symptoms and, in countries that offer it, as a screening technique for early disease - see Tests and diagnosis.

A simple bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. test, it measures the level of PSA An abbreviation for prostate-specific antigen, an enzyme that is produced by the prostate. High levels are present in the blood when the prostate gland is enlarged or inflamed. (prostate specific antigenA substance that prompts the immune system to fight infection with antibodies.) in the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid.. PSA is a protein made by the prostate glandAn organ with the ability to make and secrete certain fluids., and all men have some PSA in their bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid.. High levels can indicate prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body..

However PSA levels naturally increase with age and can be raised by benign prostate conditions, infections or even some kinds of medication.

A recent study found that obese men may have lower than average levels of PSA in their bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid., so possible cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. cases may be missed or cancers may not be detected until they are more advanced.

Testing for PSA along with urine tests and digital rectal examination (DREDigital rectal examination, physical examination that involves inserting a finger into the patient’s rectum, their back passage.) can provide helpful additional information for doctors trying to determine whether a man's symptoms may be due to prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. or to some other condition.

PSA testing is also helpful in monitoring men after prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. treatment, and in active surveillance of men who decide to avoid treatment but would like to keep their options open to have treatment in future if their PSA levels rise.

Because levels of PSA are affected by many factors other than cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body., the usefulness of the PSA test as a screening tool in men who have no symptoms is contentious.

PSA screening - for

Supporters of using PSA testing to screen men for prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. say that this is a reliable method to detect cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. in its early stages, when prompt treatment may prevent progressive disease.

They argue that mortality rates from prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. have fallen four times faster in the USA, where PSA screening is in widespread use, than in the UK, where there is no nationwide programme.

According to the American Cancer Society (ACS), 99 per cent of men diagnosed with prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. in the USA survive for at least five years. In the UK, the five-year survival rate is 71 per cent.

What's more, 91 per cent of prostate cancers in the USA are detected before they have spread to distant parts of the body, at a stage when the five-year survival rate approaches 100 per cent. In contrast, five-year survival for men with cancers that have already spread at the time of diagnosisThe process of determining which condition a patient may have. is only about 32 per cent.

The ACS therefore recommends that doctors offer PSA testing to all men aged 50 and older who are expected to live for at least another 10 years, and to men at high-risk starting from age 45.

This position is echoed by the American Urological Society, which encourages healthy men to have an annual PSA test from age 50, and high-risk men (black men and those with a family history of prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body.) to start screening tests at age 40.

PSA screening - against

However, many experts believe that there is not yet sufficient evidence to recommend universal PSA screening for older men.

The US Centers for Disease Control and Prevention (CDC) considers that the evidence on PSA screening at present is insufficient to determine whether its benefits outweigh its harms.

Testing men without symptoms may create considerable stressRelating to injury or concern. if PSA levels are found to be raised, yet most men with high PSA levels do not have prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body..

While screening will find elevated PSA levels in about 15 per cent of men aged 50 and above, only three per cent will have cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body..

So 12 in every 100 men tested are likely to be advised to have a prostate biopsyThe removal of a small sample of cells or tissue so that it may be examined under a microscope. The term may also refer to the tissue sample itself. that will not reveal cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body.. While this may be reassuring, the biopsyThe removal of a small sample of cells or tissue so that it may be examined under a microscope. The term may also refer to the tissue sample itself. procedure is stressful and uncomfortable, and even after a normal biopsyThe removal of a small sample of cells or tissue so that it may be examined under a microscope. The term may also refer to the tissue sample itself. result, many men - and their families - remain anxious about the possibility of cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body..

Furthermore, for the three in every 100 men screened who are shown to have prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body., the best choice of treatment is far from clear - see Choosing treatments. Since the majority of prostate cancers grow very slowly, for many men the benefits of treatment are outweighed by its hazards and side-effects.

Some men may choose to avoid treatment, yet remain anxious because of their knowledge of their test results, while others may opt for invasive treatment as a result of PSA screening and biopsyThe removal of a small sample of cells or tissue so that it may be examined under a microscope. The term may also refer to the tissue sample itself. when in fact their cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. would never have caused problems during their lifetime.

Another issue is that as well as raising a suspicion of cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. among many men who do not actually have it, the PSA test does not detect all cancers that may be present.

In a large-scale 2006 study in America, researchers carried out biopsies on 5,000 middle-aged men and compared the results with their PSA tests. Prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. was found on biopsyThe removal of a small sample of cells or tissue so that it may be examined under a microscope. The term may also refer to the tissue sample itself. in 20 to 30 per cent of those who had normal PSA levels - and who would have been tested by their doctors and told they were clear. This study also calls into question the reliability of PSA as a diagnostic tool.

Some experts who are cautious about promoting widespread screening also argue that comparing survival rates from prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. in the USA and UK is misleading.

Widespread screening in the USA means that more prostate cancers are detected, increasing the apparent incidenceThe number of new episodes of a condition arising in a certain group of people over a specified period of time. rate, but more of them are found at an early stage, when treatment is usually curative, and many would probably never have progressed anyway during the man's lifetime.

This inevitably makes for more favourable survival figures. In the UK, in contrast, the figures include a higher proportion of advanced cases, pulling down the survival rate.

If survival rates may be distorted by widespread screening, it may be more valid to look at men's chances of actually dying from prostate cancerAbnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body.. In fact, the annual mortality rates are much more similar: 24.8 per 100,000 men in the UK versus 26.7 per 100,000 in the USA.