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MPs on Parliament's health committee will hold an inquiry into prostate cancer screening, a move that will expose deep divisions over its worth.

Committee chairman Dr Paul Hutchison said yesterday that the committee hoped to clarify the confusion faced by some patients because of the different messages they received from the Ministry of Health and some specialists.

"The clinicians are saying the evidence is pretty clear to give men better information on early detection and improvements in early treatment."

But the ministry, unwilling to pursue a national screening programme, goes no further than encouraging GPs to explain the risks and benefits of the disease and the testing - when asked by patients.

Prostate cancer screening is controversial. Some want a national scheme like the female breast and cervical programmes; others says the screening tests - prostate specific antigen (PSA) blood tests and digital rectal examination (DRE) by a doctor - are too unreliable and many well men would be needlessly harmed.

It was long hoped that large screening trials in Europe and the United States would resolve the question but their findings are contradictory.

Auckland urologist Dr Robin Smart, writing before the latest results, said in the Medical Journal that earlier evidence in favour of screening with PSA and DRE was "overwhelming" and up to half of the 600 deaths from prostate cancer in New Zealand each year could be prevented "by the application of current technology".

He said many countries had reduced prostate cancer mortality by 10 per cent to 39 per cent by PSA/DRE screening, and diagnosis based on ultrasound with tissue biopsies.

But Otago University public health medicine specialist Dr Brian Cox said, "Most of the reduction of other countries' mortality is from better treatment, not early detection.

"It is seductively simple to think that because you detect something early you are bound to have a benefit for patients."

Doctors should tell men who asked about screening that "it's very experimental at this point".

In the journal, he and colleague Mary Jane Sneyd said the European study findings suggested a 20 per cent reduction in mortality from PSA and other tests. The US study found a 13 per cent increase in mortality in those offered annual PSA tests, but this was not statistically significant.

The European study found that for every 1480 men screened, 48 would be diagnosed with cancer and one life saved.

But for half of the 48, their cancer would not have developed into a disease of any clinical significance, and four would be left with chronic incontinence or impotence as a side-effect of treatment.

They said in the journal that the conflict between the European and US results meant the picture for PSA screening remained inconclusive.

But the Urological Society of Australia and New Zealand said the European study was good evidence for PSA testing and that the US study, because of its design flaws, should be ignored.

* Cancer debates

Screening tests for prostate cancer: blood test and digital rectal examination by doctor.

Blood test measures prostate specific antigen (PSA).

Positive cases have tissue biopsies taken for diagnosis, usually guided by ultrasound.

Main treatments for localised disease: surgery, radiotherapy, or "active monitoring" if low-risk.

Health Ministry urges doctors to explain risks and benefits of testing and disease to men who ask.

No national screening programme because of lack of evidence it will do more good than harm, although latest evidence being reviewed.

For screening

Urologist: Comprehensive testing could help prevent up to half of the 600 prostate cancer deaths in New Zealand each year.

Against screening

Public health specialists: Only modest mortality reduction likely from screening and it harms some men unnecessarily.