Doubts over prostate cancer tests

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Study suggests blood sample-based screening for men without symptoms may do more harm than good.

Prostate cancer screening using blood samples may do more harm than good, according to a European study now being cited here in favour of restrictions on the testing.

Researchers in France re-analysed results of a large European study on screening of men without symptoms with the prostate specific antigen (PSA) blood test.

The original study reported a 20 per cent fall in prostate cancer deaths for men in the screening group.

But the reanalysis included estimates on the number of deaths from prostate cancer treatment and deaths from complications, such as major infection, after biopsy tissue samples being taken from the prostate. The original study found for every 1055 men screened, 37 prostate cancers were detected and one prostate cancer death was avoided. This equated to a gain of of 9.3 years of life.

But the reanalysis, published in the journal of the British Association of Urological Surgeons, calculated screening 1055 men and detecting 37 cancers would also lead to the loss of 3.2 years of life from treatment deaths and 9.7 years from biopsy deaths. The collective loss from biopsy deaths was based on the assumption each of these men would have lived 17.1 more years on average.

The researchers said the net loss of life, for every 1055 men screened, would be 3.6 years. "It appears that screening would generate more harm - in terms of lost years of life - than good," the researchers say. "Unless the mortality rate associated with prostate biopsy can be decreased, screening for prostate cancer with PSA should be discouraged."

Associate Professor Brian Cox, a cancer epidemiologist at Otago University, said the new study was further evidence PSA testing of asymptomatic men "should be severely restricted or cease". Many of the cancers diagnosed would never cause problems in the man's lifetime.

More than 40 per cent of men over 50 in New Zealand have had PSA testing. Prostate cancer was the most commonly diagnosed cancer in 2009, with 3369 new cases. It was the third most common cause of cancer death for men, with 562 deaths.

The prostate is a gland the size of a golf ball in front of the rectum. It produces some of the fluid in semen.

The Government has not set up a screening programme because of the uncertainties about PSA testing. The Health Ministry urges doctors to provide "balanced information on prostate cancer and the possible benefits and harms of testing and treatment".

The Urological Society of Australia and New Zealand says men aged 55 to 69 should be offered PSA testing and digital rectal examination.

Professor Cox said screening programmes were based on the principle of participants' average chance of benefiting exceeding the chance of harm.

"This report suggests someone who doesn't have symptoms having PSA testing probably has a greater chance of shortening their life than lengthening it."