shown to be efficacious in at least one RCT, but these screening
tests have thus far not been shown to be effective in practice.
It is most important to note that the Papanicolaou (Pap)
smear screening test for cervical cancer has been used very
successfully in practice in many countries that have
introduced regular repeated Pap smear population-based
screening.6 Most importantly, in contrast to breast cancer
screening, which is secondary prevention, the Pap smear
screening test detects cancer precursors that can be
successfully treated and therefore reduces cervical cancer
mortality by first reducing incidence (primary prevention).
However, a "once in a lifetime" Pap smear was not efficacious
in the only reported RCT in which it has ever been tested. This
4 arm RCT compared "once in a lifetime" Pap smear versus a
HPV virus test of cervical cells versus VIA, followed by
referral of test positive women for further diagnostic tests
and treatment, versus an observation only arm (controls).8
Only those women screened with the HPV test had a
significant reduction in cervical cancer mortality as compared
to the controls.
Breast cancer, with 1.7 million new cases, 12% of all global
cancers, and 520,000 deaths in 2012, is the commonest
potentially fatal cancer of women and its incidence has been
increasing worldwide for decades.
10 There is currently at least
a four-fold variation in age-standardized incidence rates
between countries with the lowest (east and southern Africa)
and countries with the highest (Western Europe, North
America and Australia/New Zealand) rates. Furthermore, it is
potentially one of the most curable of cancers. However, fiveyear
relative survival rates worldwide currently cover a
seven-fold range based on analysis of data from cancer
registries: from 13% in Gambia to 46% in Uganda to 57-66%
in Thailand to 60-80% in Europe to 70% in Cuba and Costa
Rica to 88% in Australia and 92% in the United States.11-14
Breast cancer mortality trends are available for many highincome countries, mostly European, North American and
Asian: Korea, Japan, Australia and New Zealand. After being
on a plateau for decades breast cancer mortality began falling
in a number of those countries about 1990, although in some
countries, such as Sweden, this fall began as early as 1975.15
These declines in breast cancer mortality have mainly
occurred in countries where either or both of two
interventions were introduced:
‰ endocrine and/or chemotherapy administered
immediately after the primary surgical treatment
(adjuvant therapy);
‰ mammographic screening (secondary prevention).
Early breast cancer is defined by the Early Breast Cancer
Trialists Collaborative Group (EBCTCG) as "loco-regional
breast cancer that can all be removed surgically".
16 The
EBCTCG have, since 1988, been publishing five-yearly
systematic reviews of adjuvant endocrine and chemotherapy
for breast cancer and advised in 2005 that "allocation to
about six months of anthracycline-based poly-chemotherapy
reduces the annual breast cancer death rate by about 38%
for women aged under 50 at diagnosis and by about 20% for
those aged 50-69 years; and that for ER-positive disease
only, at any age, allocation to about five years of adjuvant
tamoxifen reduces the annual breast cancer death rate by
31%. These effects were each seen irrespective of other
treatment or tumour characteristics".16
At the end of the twentieth century the message was clear:
in countries with a significant breast cancer burden that also
had a sufficient level of resources, implementing a
population-based mammographic screening programme
could reduce breast cancer mortality in women aged 50-69
years by about 25%. This is well covered in the WHO
International Agency for Research on Cancer (IARC)
monograph on breast cancer screening.3 Most importantly, all
the RCT, which are the basis for this recommendation3 were
completed at a time when few women received adjuvant
endocrine and/or chemotherapy (adjuvant therapy) that can
cure many women with early breast cancer.17,18
Therefore, mammographic screening is now very
controversial. Kirwan wrote in the British Medical Journal
(BMJ) in 2013: "In the past 12 months alone the BMJ, the
Lancet and New England Journal of Medicine have published 24
articles or communications debating the value of breast
cancer screening".19 In theory, screening asymptomatic
women for an earlier and more treatable form of a potentially
fatal disease like breast cancer should reduce all-cause and
breast cancer specific mortality, although screening always
has intrinsic harms (see later). However, this will not occur if
screening is ineffective because it is opportunistic/ad-hoc or
population-based but poorly organized with low
participation. Screening will also fail if the treatment of the
disease at early and later stages improves so that earlier
DISEASE-SPECIFIC CANCER CONTROL
CANCER CONTROL 2014 99
Breast cancer, with 1.7 million new
cases, 12% of all global cancers, and
520,000 deaths in 2012, is the
commonest potentially fatal cancer of
women and its incidence has been
increasing worldwide for decades