University of Cambridge

Date: 02/04/09

Prostate screening may have benefits

Cambridge University scientists have shown that screening for prostate cancer using prostate specific antigen (PSA) would lead to a reduction in advanced stage prostate cancer by up to 54 per cent.

However, there would be likely overdiagnosed cases of prostate cancer according to a study published in the British Journal of Cancer this week.

The researchers studied 43,842 healthy men given PSA testing as part of the ProtecT study to calculate the number of advanced stage prostate cancers picked up as a result of the testing. They also worked out the length of time during which prostate tumours do not produce symptoms but are detectable by a screening test - the mean sojourn time (MST).

The MST test is a method of calculating 'overdiagnosis' and was used to estimate the probability of a diagnosis which would not have caused symptoms during the patients lifetime if screening had not taken place.

In the study, 1,544 men aged 50-69 were diagnosed with prostate cancer through the PSA testing . Overdiagnosis was estimated at one in 10 in the 50-59 age group and increased to three in 10, (31 per cent) in the 60-69 age group.

Study author, Dr Nora Pashayan, a Cancer Research UK scientist at the University of Cambridge said: "Our results indicate a benefit of screening to reduce the risk of advanced stage prostate cancer. However, this is limited by overdiagnosis. Any screening strategy should take account of the potential benefits and harms of screening. A valuable target for future research would be to estimate the benefit of screening at different ages."

Prostate cancer can be slow-growing or aggressive. Men with a non aggressive form may not develop symptoms for many years and not always need treatment - the side effects of treatment can be significant. But the difficulty is that on diagnosis, doctors can not always tell which forms of prostate cancer are aggressive and which are slow growing.

Lead author Professor David Neal, based at Cancer Research UK's Cambridge Research Institute, said: "Overdiagnosis is a real concern. There is currently no way to tell whether a prostate cancer is aggressive, or passive. Until a test has been developed to distinguish between these, we would prefer to avoid treating patients who don't need treatment which can lead to unnecessary side effects like impotence and incontinence. It is important that men in their 50s and 60s feel able to talk to their doctors and request a PSA test if necessary."

There is no prostate cancer screening programme in the UK but there is ongoing ad-hoc testing. Screening with PSA alone is not yet recommended in the UK because there is not yet firm evidence that screening reduces mortality from the disease.

Prostate cancer is the most common cancer in men in the UK - more than 34,000 men are diagnosed each year and 60 per cent of cases are diagnosed in men over 70. Around 70 per cent of newly diagnosed prostate cancer patients live longer than five years.

Reproduced courtesy University of Cambridge Office of Communications

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Organisation: University of Cambridge

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