Screening older men with the PSA blood test could cut prostate cancer deaths by around half, according to a new study. However, this finding must be considered alongside previous studies, which have found modest or nonexistent benefits.

What do we know already?

There’s lots of disagreement among doctors about whether screening for prostate cancer is worthwhile. The usual test, which looks for increased levels of a chemical called PSA in the blood, isn’t very accurate. PSA levels have to be very high to give a clear indication of cancer, and very low to rule cancer out. Most men score somewhere in the middle.

Another problem with screening is that prostate cancer is often slow growing. About half of 80-year-old men have cancer cells in their prostate, but only 1 in 25 will die of prostate cancer. The rest will have a type of cancer that’s so slow growing it will never do them any harm.

There’s not an easy way to tell slow- from fast-growing prostate cancers. So why not treat all cases then, just to be safe? That would mean men with slow-growing cancers got surgery or radiotherapy they didn’t need, putting them at risk of unpleasant side effects such as incontinence or erection problems.

As things stand, there’s no clear answer about whether using the PSA test to screen for prostate cancer saves lives. Some large studies show a small benefit, and others don’t. A new study has looked at how well PSA screening worked for 20,000 men living in Sweden.

What does the new study say?

Men who were offered screening were less likely to die of prostate cancer than men who weren’t.

Screening cut prostate cancer deaths by nearly half. Of the 10,000 men who were offered screening, 44 of them died of prostate cancer. Among the 10,000 men who weren’t offered screening, 78 died of prostate cancer.

Although screening did seem to save lives, the problem of unnecessary treatment remains. The study found that 293 men needed to be screened and 12 diagnosed with prostate cancer to save one life.

How reliable is the research?

The study was done well, but so were two previous studies, one of which found that screening only cut prostate cancer deaths slightly, with the other finding that screening didn’t save lives at all. Why the different results?

The two previous studies were much bigger than this one. In fact, the new study looks at a subgroup of men from one of the previous studies. However, they’ve now been followed up for longer (14 years, compared with 9 and 11.5 years in the previous studies). The researchers think that any benefits from screening are only evident after the first 10 years, which may be why this study got better results from screening.

Another difference is that, in the new study, even moderately high PSA test results were followed up with a biopsy (which removes some cells from the prostate and checks them for cancer cells). Previous studies used a higher cut-off point for PSA results, so men were less likely to have follow-up tests.

In the new study, men were invited for screening every two years, as opposed to every year or every four years in the previous trials.

Men in the new study were also younger on average than in previous studies.

Where does the study come from?

The study was published in The Lancet Oncology, which is owned by a company called Elsevier. Funding came from the Swedish Cancer Society, the Swedish Research Council, and the National Cancer Institute.

What does this mean for me?

The new study shows that PSA screening for prostate cancer may save lives, but this result has to be considered together with previous studies suggesting smaller or nonexistent benefits. There’s also the problem of lots of men being given unnecessary treatment and suffering unnecessary side effects. PSA screening is likely to be controversial for some years to come.

The researchers say that, since the benefits of screening only materialise after 10 years, it may be less helpful for older men.

What should I do now?

If you’re offered a PSA test, make sure you talk to your doctor about the benefits and risks. There’s a chance that the test could help detect an aggressive tumour early enough for treatment to be successful. But there’s also a chance that the test will find a slow-growing cancer that will never harm you.

There’s no organised PSA screening programme in the UK, although your GP may recommend the test if he or she thinks it might be useful. There are also private clinics that offer PSA screening.