Pondering the PSA test

Scientists are trying to work out how effective the PSA test is

Many older men in the UK take a blood test that measures the level of a protein called PSA, which can indicate the presence of prostate cancer.

Many people argue that the PSA test should be used as a national screening programme for the disease. But how reliable is it?

The PSA test isn’t a foolproof detection method for the disease – around one in five men with prostate cancer have a normal PSA reading. And up to two-thirds of men with high PSA levels don’t have cancer.

Furthermore, it’s difficult to tell if a cancer detected using the PSA test is growing fast and needs treatment, or if it is a slow growing prostate cancer that is safe to be left untreated but closely monitored. Treatment for prostate cancer carries a small but significant risk of impotence or incontinence so there is a risk of giving treatment that may not be necessary.

Now a paper from a team of French researchers, published in the journal European Urology, has suggested that a man’s PSA level may fluctuate naturally with the seasons. They measured PSA levels in more than 8,500 men aged 55-70, and found that the more sunshine a man got, the higher his PSA.

In fact, in the summer, men’s PSA levels were raised to the point where they had a 23% greater chance of being sent for a biopsy for suspected cancer than the rest of the year. This adds to the complexity of the situation around the reliability of the PSA test for screening for cancer.

At the moment, men can ask their GP for a PSA test. The NHS has introduced the “Prostate Cancer Risk Management Programme” – a strategy enabling men to make informed choices about PSA testing. But we don’t know much about what men actually think of the test, and the uncertainties that surround it.

In order to understand more about men’s views of the PSA test, we funded Dr Joan Austoker and her team at the Cancer Research UK Primary Care Education Research Group to carry out an interesting study, published recently in the British Journal of General Practice.

The team interviewed 28 men aged 40-75, recruited from 6 GP practices in Wales, who had recently had the PSA test, or been offered the test and turned it down.

They found that men’s knowledge of the PSA test is mainly influenced by their social networks, such as neighbours or family. In a slightly skewed version of “keeping up with the Joneses”, one man commented that

“We had a neighbour move in just below us, and he told us that he’d actually had prostate cancer, and that he’d had an operation which apparently cured it; and since, has had no more problems. He said that it showed up by having what’s known as a PSA test, which I knew nothing about, so I asked the local doctor and he said, yes it was possible to have the test.”

Although men knew about the test, the researchers found that the decision to actually have it or not was mainly led by their doctor. As this man said,

“I know my doctor very well. He’s been treating me now since I left the army. He suggested a blood test, and I said fine. He didn’t have to go into the details.”

Another put it slightly more obliquely,

“Well I suppose it’s like going into a church. You put your umbrella in the corner and let the priest get on with it quite frankly.”

The study also showed that men were uncertain about things before the test, for example about what the result might mean. There was uncertainty once the results came through, which caused unhappiness and stress, even if the result was normal.

And men with raised PSA found it very distressing, especially if they were then found to have cancer. One man even said

“I think in retrospect, I wish I hadn’t [had the test]. I would say, get very well briefed on what happens if the result of the test is borderline or potentially problematic. Be sure you know what you are letting yourself in for.”

Dr Austoker’s work shows that information for men considering the PSA test needs to be very clear, and take into account these uncertainties and influences. Her research was funded by Cancer Research UK, and is part of the work to develop Prosdex – a web-based decision explorer.

There’s more about the PSA test on CancerHelp UK.