Screening 'does not prevent prostate cancer deaths', 20-yr study concludes

In collaboration with Adfero

Population-wide screening using the prostate-specific antigen (PSA) test would not help to reduce the number of deaths from prostate cancer, a Swedish study suggests.

PSA is a protein made by the prostate that is sometimes elevated in men with prostate cancer.

However, it is currently unreliable as a screening tool, as men with normal PSA levels can still have prostate cancer, while PSA may rise as a result of non-cancerous prostate conditions, sexual activity, infection or vigorous exercise in men who are cancer-free.

The latest research from Sweden's Karolinska Institute, published in the British Medical Journal, provides further information to add to the ongoing debate.

Researchers analysed data on 9,026 men, aged 50 to 69 years, who took part in a trial that started in Sweden in 1987.

Of these, 1,494 were randomly chosen to have screening every third year between 1987 and 1996, while the remaining men did not undergo screening.

Those who had screening underwent digital rectal examination - where a doctor examines the prostate via the back passage - on their first two visits, and this exam was combined with PSA testing from 1993 onwards.

The researchers followed all men who were diagnosed with cancer before the end of 1999 until December 2008.

Their analysis revealed that 5.7 per cent of men in the screening group were diagnosed with prostate cancer, compared with 3.9 per cent in the control group.

Tumours in men who were screened tended to be smaller and were less likely to have spread than those found in the control group. This suggests that screening helped to detect prostate cancers at an earlier stage.

Despite this, survival was not significantly longer or more likely for men in the screening group.

Furthermore, the researchers pointed out that screening could increase the risk of over-diagnosis and over-treatment, which can cause harmful side-effects.

This is because many of the small prostate tumours detected by screening are slow-growing and unlikely to cause any problems during the patient's lifetime. At present, there is no way of telling the difference between harmless, slow-growing tumours and more aggressive ones that need treatment.

To support their claim, the researchers cited a previous study suggesting that 1,410 men would need to be screened and 48 treated to prevent one death from prostate cancer.

The study authors wrote: "After 20 years of follow-up, the rate of death from prostate cancer did not differ significantly between men in the screening group and those in the control group."

Professor Malcolm Mason, Cancer Research UK's prostate cancer expert, commented: "This trial found that screening did not reduce deaths from prostate cancer and there is no escaping from the fact that we need a better tool than PSA to help detect prostate cancers that actually need treating, as opposed to innocent ones that do not.

"This study adds to the debate on prostate cancer screening. It re-emphasises that screening using PSA testing and digital rectal examination will detect a large number of prostate cancers that don't need treatment. But, once diagnosed, the cancer will be treated, sometimes leading to men suffering significant side-effects.

"In the meantime, men should be fully informed about the pros and cons of having their PSA measured."

References

Sandblom, G., Varenhorst, E., Rosell, J., Lofman, O., & Carlsson, P. (2011). Randomised prostate cancer screening trial: 20 year follow-up BMJ, 342 (mar31 1) DOI: 10.1136/bmj.d1539