October 2017 April 2015 | Page 15

Te Puawai
In February 2015 Lynda Williams travelled to
Sydney
for
the
weekend to hear
presentations by Don Benjamin, Convenor
and Research Director of the Cancer
Information & Support Society in Sydney, and
Professor Peter Gotzsche, Director of the
Nordic Cochrane Centre in Denmark, on
cancer screening.



All causes include cancer mortality and
non-cancer mortality.



Non-cancer mortality should not
affected by screening or treatment.

be

After showing that RCTs revealed that
“getting it all” has no proven effect on survival
or mortality, Don then went to show that early
surgery was equally ineffective.

Don Benjamin
In his presentation Don Benjamin outlined the
principles of running and interpreting results
from randomised controlled trials, summarised
the results of breast, bowel, prostate, lung,
and ovarian cancer screening trials, and
summarised the levels of overdiagnosis
resulting from cancer screening.
He began with a brief history of cancer
treatment and then described the old cancer
paradigm – cancer is a systemic disease, so
identify and treat causes, and then examined
the new paradigm – cancer starts locally and
later spreads so “get it all, and get it early.”
Before it can be assumed that cancer
interventions,
particularly
surgery
or
screening, are effective it is necessary to
provide reliable evidence of benefit. Of
course, the gold standard of evidence is the
randomised controlled trial (RCT) which Don
Benjamin went on to talk about in some
detail.
And this is where it gets tricky and
somewhat confusing, especially when it
comes to measuring efficacy. In answer to
the question what do the results of a well-run
randomised controlled trial
evaluating
treatment look like, Don said:



“In 1996 I analysed the results of the seven
RCTs evaluating breast cancer screening
and concluded that screening does more
harm than good:


Screening does not reduce overall (all
cause) mortality



Radiotherapy was used differently in the
screened and control groups (in breach of
the RCT rules)



This meant that many women who would
have died from breast cancer instead died
from heart failure making it appear that
there had been a reduction in breast
cancer deaths (confounding factors).

This lack of proof of overall benefit was
subsequently confirmed in 2001 by Peter
Gotzsche and by William Black et al in 2002.”
Don then described how RCTs have also
revealed the lack of efficacy of early surgery
– as a result of screening – for lung cancer,
prostate cancer, ovarian cancer and bowel
cancer. He ended his presentation by
discussing the harms of screening in terms of
both overdiagnosis and the resulting
overtreatment.
In summary:

After a trial is completed the number
of deaths from all causes in the treated
group is compared with the number of
deaths from all causes in the control
(untreated) group.

© Te Puawai

“There are significant benefits from screening
for breast, bowel, lung, prostate or ovarian
cancers.

College of Nurses Aotearoa (NZ) Inc
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