The PSA test is a blood test which helps to detect prostate cancer. How does it work, how effective is it and what are the pros and cons of having it done?

This article on the PSA test and prostate cancer is written by Sarah Dawson, a freelance journalist who writes for national and international newspapers, magazines and websites.

Prostate Cancer is the most common cancer affecting men in the UK, with nearly 32,000 new cases diagnosed each year, but it is rarely found in men aged below 45 - four out of five prostate cancers are diagnosed over the age of 65. Prostate Cancer is different to other cancers because it tends to grow slowly so a patient can have it for years and not even know about it, as there often aren't any symptoms. It's when the cancers are large enough that they press on the urinary tube (urethra) disturbing the bladder that a man may be prompted to visit his GP.

There are a number of factors which are believed to increase the likelihood of prostate cancer including race, age, diet and genetics. Having a relative (brother, uncle or father) who has/had prostate cancer put you at a slightly higher risk, and research suggests that Afro-Caribbean and African-American men tend to be more affected than white men, with prostate cancer rare in men in the Far East.

A man's risk increases the older he is, and cases of prostate cancer tend to appear more in countries where people eat a lot of fat. Studies show that following a low-fat vegetarian diet, with plenty of Vitamin E, selenium and lycopenes-rich vegetables like tomatoes offers protection against prostate cancer. In most cases, prostate cancers grow slowly and don't spread to other parts of the body so the cancer may never need to be treated. According to the NHS by the age of 80, half of all men will have some cancer cells in their prostate, but only one in 30 will die from it.

The walnut-shaped gland

The prostate gland is positioned beneath a man's bladder near the rectum (back passage), and is shaped like a walnut. It produces semen and a protein called Prostate Specific Antigen (PSA) which liquefies the semen and mixes with sperm made by the testes. Because small amounts of PSA are found in the blood, the PSA Test can highlight prostate activity and check for raised levels of PSA - which could indicate prostate cancer. However, there is much speculation about how effective this test is.

Quite often a raised PSA level can be attributed to a less serious condition, for example, an inflamed prostate - a condition known as prostatitis, or an enlargement of the prostate known as benign prostatic hypertrophy (BPH) which typically affects men aged over 50. With BPH a man will have difficulty passing urine, feel like he needs to pass urine more often (especially at night), experiences pain when passing urine and has occasional blood in urine or semen. Prostatitis has similar symptoms and is often caused by an infection or an injury and is treatable with antibiotics. Neither condition is linked to prostate cancer despite the symptoms being similar. A high PSA level could also indicate an infection, a recent prostate biopsy, a urinary catheter (a tube to drain urine), prostate or bladder surgery, prolonged exercise such as long-distance running/cycling, or even ejaculation.

To have or not to have

The debate about the PSA test is ongoing. According to the NHS, two out of three men with a raised PSA will not have any cancer cells in their prostate biopsy and up to one in five men with prostate cancer will have a normal PSA result. Along with not being able to tell whether a prostate cancer is present, health professionals also don't believe a PSA test can tell whether the cancer is slow or fast growing. There is also no conclusive evidence that screening improves a man's chance of survival due to the number of false positive results.

With such uninspiring statistics, it's not surprising that many men don't bother taking the PSA test, preferring not to know if they have an early prostate cancer because knowing wouldn't necessarily help their case. Some men decide that they would like to do the PSA test and to treat prostate cancer if it occurs, but the health services don't believe that a PSA screening programme for all men would cut deaths from prostate cancer - even though there is demand for the test.

False alarms and needless anxiety

Before taking the PSA test men should weigh up the pros and cons of doing so. The government has developed a Prostate Cancer Risk Management programme with a printable guide to help them make a well-considered decision. The guide explains that the older a man is the higher his PSA reading will be, regardless of whether or not he has prostate cancer. By way of example, the NHS guidelines suggest that a man aged 50 is likely to have a PSA reading of 2.8 nanograms (a billionth of a gram) per millilitre of blood. 'Normal' means that he is unlikely to have prostate cancer. If it is slightly raised, then he is advised to have another test in a few months. If the PSA level is significantly raised then a biopsy (a sample of tissues) is taken and sent to a laboratory for further examination.

There is doubt about whether treatment is necessary for early prostate cancer. The majority of prostate cancers grow slowly and the side effects of the cancer treatment could be far worse than the effects of the cancer. However, there are some types of prostate cancer which grow faster and spread to other parts of the body, via the bloodstream to the bones. But experts believe that screening programmes can cause false alarms and create needless anxiety so until it is proven that a national screening programme will bring more benefit than harm, the NHS isn't inviting men without symptoms for prostate cancer screening.

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