Many men in New Zealand are suffering side effects after
radiotherapy and surgery for prostate cancer which would
never have killed them, and a screening programme would
increase this, University of Otago public health researcher
Dr Brian Cox says.
He was commenting on the recent announcement by chairman of
the Health Committee Dr Paul Hutchison that the committee
will conduct an inquiry into optimal screening (or early
detection) and treatment of prostate cancer.
Dr Cox is concerned there is already considerable over
treatment of men for this disease with very little evidence
of any reduction in deaths from it.
The issue of prostate screening has been controversial, with
some proponents of it suggesting that the disease has
received less attention than women's diseases such as breast
and cervical cancer both of which have screening programmes.
This argument does not wash with Dr Cox, who says there is
still no evidence that a screening programme would be
beneficial.
"Were not withholding something from them which does work."
It did not make sense to do something which would increase
peoples risk "if you are offering something which has a
considerable hazard, you have really added to their
problems".
The difficulty was that the commonly used prostate specific
antigen test (PSA) led to over-diagnosis of cancers and over
treatment.
About 30% of men over 50 had a small tumour on their prostate
which, when studied under a microscope was indistinguishable
from cancer.
A vast majority of these tumours did not appear to become a
clinical disease or even cause symptoms.
Research into randomised trials using PSA for screening
showed that the over-diagnosis of cancers could be as high as
50%.
Men were undergoing radical prostatectomy or radiotherapy
which could result in chronic incontinence (urinary or
faecal), impotence, or in some instances, death, he said.
Dr Cox estimates that about 2000 cases of prostate cancer are
detected by PSA testing a year in New Zealand and about half
of them would never become clinically relevant.
Results of a recent European randomised trial showed 1480 men
would need to be screened and 48 additional cases of prostate
cancer treated for each death prevented over a 10-year
period.
About half of those additional cases would be receiving
treatment for something which would not have become clinical
prostate cancer in their lifetime, and about four of them
would have chronic incontinence or impotence.
Dr Cox said he was looking forward to seeing the terms of
reference for the inquiry and hoped that the committee wanted
to seriously consider all the information and not push
through a political agenda.
Dr Hutchison said he was aware the situation was
controversial and some clinicians were frustrated about the
current guidelines, particularly as they considered there was
benefit in testing those considered at higher risk.
Recent research findings were another reason for his decision
to look at the situation again.
He was anxious to get as much factual information as he
could.
Prostate cancer in NZ
583 deaths from prostate cancer in 2004.
2693 new registrations in 2004.
Death rate 1995-2002, 18-20 per 100,000; dropped slightly to
16.6 by 2004.
Two-thirds of deaths in men 75 or older.
PSA test
Prostate specific antigen test measures the level of this in
the blood.
Levels can be raised by urinary or prostate infection,
enlarged prostate, prostate cancer or other reasons including
recent ejaculation.
There is no absolute PSA level that detects a cancer.
Screening
Using PSA or digital rectal examination for men without
symptoms -
Ruled out by National Health Committee in 2004.
Potential for benefit did not outweigh harm.
There was no suitable test.
