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Four papers appear in the print BMJ this week in abridged form. The full and abridged versions are both available here on our website. The editorial by Delamothe et al explains why we are doing this, and we welcome readers' reactions. The paper by Whitehead (p. 908) appears in two abridged versions, one much shorter than the other; again we welcome readers' reactions on which they prefer, and why.
Mike Quinn National Cancer Registration Bureau, Office for National
Statistics, Demography and Health Division, London SW1V 2QQ
Correspondence to: Dr Quinn
mike.quinn{at}ons.gov.uk
Objective:
To assess the impact of screening on the
incidence of and mortality from cervical cancer.
Invasive cervical cancer is the second most common cancer in women
worldwide, but 80% of cases occur in developing countries. The
incidence of the disease has been falling in many western countries,
but not in Great Britain, over the past 40 years. The cervical smear
test was developed over 50 years ago, and screening began in Great
Britain, some Nordic countries, and parts of North America in the 1960s.
In the late 1980s the incidence of cervical cancer in Great Britain was
in the middle of the European range. But mortality was among the
highest of the developed countries, and in Europe only Denmark had a
higher rate. Survival improved slightly in England during the
1980s,1 but remained worse than in most other European
countries.2 It is much poorer for later than earlier stage
disease.3
A link between cervical cancer and a sexually transmitted infection was
first suggested because it was associated with women who had had many
sexual partners, or whose partner had, and an early age at first
intercourse.4 Evidence for the aetiological role of human
papillomavirus has accumulated from both molecular and epidemiological
studies.5 Other risk factors include smoking, oral
contraceptives, parity, cervical trauma during childbirth, and hormonal
influences of pregnancy.6 Changes in these risk factors
over time will have affected the incidence of cervical cancer.
Although cervical screening in England started in 1964, for over 20 years it failed to achieve sufficient coverage of women or follow up of
all women with positive results.7 During the 1980s,
several recommendations were made to improve the screening programme,
and in 1987 an intercollegiate working party recommended that screens
be repeated every three years for women aged 20 to 64 years.8 A national call and recall system was established in 1988.9 In 1996, 60% of district health authorities
operated a 3 year recall.10 Financial incentives were
first introduced with general practitioner contracts in
1990.11
To assess the impact of the screening programme in England we examined
trends in the numbers of smears taken and other characteristics of the
screening programme; age specific trends for both in situ and invasive
cervical cancer from 1971 to 1995; and age specific mortality from
cervical cancer from 1950 to 1997.
The target age group for screening is 20 to 64 years; coverage is
defined from 1995 onwards as the percentage of women aged 25 to 64 who
had had a smear test in the previous 5 years (for 1988 to 1994, the
previous 51/2 years).12 The cancer registration system has been described elsewhere.13 Both the
ascertainment and quality of data from cancer registries in Great
Britain are generally high.14
Data on registrations of in situ and invasive cervical cancer from 1971 to 1991 are based on records of individual cases submitted to and
validated by the Office for National Statistics.13 Figures for 1992 to 1995 are based on annual data supplied by the regional cancer registries (from cases that had been validated by the registries and aggregated into 5 year age groups). Only small overall differences exist between the two types of data.15 For the two regions
for which data were not available for 1993 to 1995, we assumed that the
age specific incidence changed by the same amount as the average change
in those regions for which data were available. Information on the
stage of invasive disease was not available centrally.
We used published data on mortality from cervical cancer for 1950 to
1997. Although there have been three changes in the international classification of diseases over this period, no substantial alterations have occurred relating to cervical cancer. We adjusted the mortality data to allow for procedural changes in the coding of cause of death.15
The registrations of in situ cervical cancer are not true incidence
because, firstly, the disease is asymptomatic and cases are detected
only by screening. Thus any changes over time in the number of women
screened in different age groups will affect the numbers of
registrations. Secondly, as women are not all screened annually,
registrations are a mix of cases diagnosed in women screened for the
first time and cumulative incidence since the previous screen for women
who have been screened before.
The annual age specific rates for both incidence and mortality were
calculated as the numbers of cases divided by the estimated mid-year
population. Summary rates for incidence and mortality were directly age
standardised by using the European standard population (5 year age
bands). Confidence intervals for age specific and age standardised
rates were calculated on the assumption that the number of cases
followed a Poisson distribution16; the figures show
typical 95% confidence intervals.
Screening programme
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Abstract
Top
Abstract
Introduction
Subjects and methods
Results
Discussion
References
Design:
Comparison of age specific incidence and
mortality before and after the introduction of the national call and
recall system in 1988.
Setting:
England.
Subjects:
Women aged over 19 years.
Results:
From the mid-1960s, the number of smears
taken rose continuously to 4.5 million at the end of the 1980s. Between 1988 and 1994, coverage of the target group doubled to around 85%.
Registrations of in situ disease increased broadly in parallel with the
numbers of smears taken. The overall incidence of invasive disease
remained stable up to the end of the 1980s, although there were strong
cohort effects; from 1990 incidence fell continuously and in 1995 was
35% lower than in the 1980s. The fall in overall mortality since 1950 accelerated at the end of the 1980s; there were strong cohort effects.
Mortality in women under 55 was much lower in the 1990s than would have
been expected.
Conclusions:
The national call and recall system and
incentive payments to general practitioners increased coverage to
around 85%. This resulted in falls in incidence of invasive disease in all regions of England and in all age groups from 30 to 74. The falls
in mortality in older women were largely unrelated to screening, but
without screening there might have been 800 more deaths from cervical
cancer in women under 55 in 1997.
Key messages
![]()
Introduction
Top
Abstract
Introduction
Subjects and methods
Results
Discussion
References
![]()
Subjects and methods
Top
Abstract
Introduction
Subjects and methods
Results
Discussion
References
![]()
Results
Top
Abstract
Introduction
Subjects and methods
Results
Discussion
References
The number of smears taken rose by about 6% each year until the
early 1980s, after which the increase was about 8% each year to the
end of the decade; since then, about 4.5 million smears have been taken
each year (fig 1).
12 17-19
The coverage of the target
age group in the screening programme rose from 42% in 1988 to 85% in
1994, a level subsequently maintained (see fig 3).12
Coverage increased in all age groups, but particularly for older women
(55 to 64 years).

View larger version (27K):
[in a new window]
Fig 1.
Number of cervical smears and directly age
standardised rate of in situ cervical cancer, England, 1965-95
Carcinoma in situ
The registration rate of carcinoma in situ rose broadly in line
with the increasing numbers of smears taken, from about 10/100 000
women (2100 cases) in 1971 to 80 per100 000 (20 000 cases) in the
mid-1990s (fig 1). The apparent large increase in the rates in 1984 and
1985 is due to the inclusion for the first time of registrations of
cervical intraepithelial neoplasia grade III. Since 1987 the trends in
registrations in women aged 20-24 and 25-29 have been continually
upward, whereas women aged from 30 to 49 have shown no overall increase
(fig 2). Registrations for older groups were consistently low and fell with age.
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Invasive cancer
From 1971 to the mid-1980s incidence remained between 14 and
16/100 000 (on average 3900 cases a year) (fig 3). It fell for five
consecutive years after 1990, reaching just over 10/100 000 in 1995, about 35% lower than in the mid-1980s. The 2900 cases diagnosed in
1995 represented 3% of all malignancies (excluding non-melanoma skin
cancer) in women. Age specific incidence has, however, changed
differently in the various age groups (fig 4). In 1995, the overall
pattern was similar to that in 1990, but the incidence in every age
group from 30-34 to 70-74 was substantially (and significantly)
lower
by an average 9/100 000 (110 cases).
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Mortality
From 1950 to 1987 total mortality from cervical cancer fell
steadily by just over 1.5% each year, from 11.2/100 000 (2500 deaths)
to 6.1/100 000 (1800 deaths). The rate of fall then trebled, and by
1997 mortality had fallen to 3.7/100 000 (fig 5). The 1150 deaths in
1997 represented 2% of cancer deaths in women and 0.4% of all deaths
in women.
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that is, women
born in the mid-1950s
mortality was three times higher than it had
been for women aged 25-34 in the mid-1960s.
20 21
Cervical
cancer mortality in each birth cohort historically increased with age
up to 60 years.21 If the raised risk and pattern of mortality are assumed for women born in the mid-1950s, by 1997 mortality would have increased to around 14/100 000 in women aged 35 to 44, and (with a similar projection based on a doubling of mortality
for the cohort born in the mid-1940s) to around 19/100 000 in women
aged 45 to 54. These rates are far higher than those actually observed
(around 5/100 000 in both age groups (fig 6)). Applying the difference
between the projected and actual mortality in 1997 to the number of
women in each age group suggests that screening might have prevented
320 deaths in women aged 35-44 and 430 deaths in women aged 45-54. In
addition, mortality in women aged 25-34 in 1997 was one third lower
than in the peak in the mid-1980s so a further 50 deaths may have been
prevented in this age group.
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Discussion |
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Screening programme
Cervical screening by the smear test meets some of the criteria
for screening programmes laid down by the World Health
Organisation,22 but not the two which are probably the
most important: cervical cancer in England is relatively uncommon and
its natural course is not well understood. Although the effectiveness of screening has never been properly demonstrated in randomised controlled trials, firm evidence comes from the Nordic countries, where
the implementation of widely different policies resulted in sharply
contrasting trends in incidence and mortality.23 Even so,
many operational features of the cervical screening process in England
have been heavily criticised.
10 24
26
there is little benefit, but enormous
increase in costs in opportunistic screening at shorter intervals than
those recommended.
10 23
It would also be possible to
reduce costs by not screening women under 25 and by not continuing to
screen women over 50 who have had two or three consecutive normal
results.
27 28
Screening women over 65, particularly those
who have never had a smear, could, however, reduce mortality through
diagnosis of cancer at an early stage.29
Wilkinson et al have suggested that targeting high risk groups might
improve the effectiveness of screening,30 but the four high risk categories considered have fairly low odds ratios. Women at
increased risk would therefore comprise a large proportion of the
population, and the resulting stigmatisation would be socially unacceptable.
Effectiveness
Before the introduction of the national call and recall system and
of incentive payments to general practitioners the cervical screening
programme in England was largely ineffective, owing mainly to problems
of organisation.
7 10 23
Most cytological tests were
performed on women presenting for obstetric, gynaecological, or
contraceptive reasons. At least two thirds of women with invasive cervical cancer had never been screened; for women over 40 (among whom
70% of cases occurred) over 90% had never been
screened.31
Mortality
Interpretation of trends in mortality data presents several
problems. Firstly, mortality may be affected by changes in survival.
But there have been no significant improvements in treatment for
cervical cancer over the past 20 years, and there is no evidence that
stage specific survival rates have improved substantially. Secondly,
recording of cause of death may not always be accurate, and attempts to
improve death certification may lead to artefactual changes. Thirdly,
the proportion of deaths ascribed to "cancer of the uterus, site
unspecified" has varied32 and will have decreased as
death certification improved.
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Acknowledgments |
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Members registries (directors) of the United Kingdom Association of Cancer Registries are: East Anglian (C H Brown, T W Davies), Information and Statistics Division of the NHS in Scotland (D Brewster), Merseyside and Cheshire (E M I Williams), North Western (C B J Woodman), Northern and Yorkshire (D Forman), Northern Ireland (A Gavin), Office for National Statistics (M J Quinn), Oxford (M Roche), South and West (J A E Smith), Thames (G Matthews), Trent (J Botha), Wales (J Steward), West Midlands (G M Lawrence).
We thank Michel Coleman, Tim Devis, Karen Dunnell, and John Fox at the Office for National Statistics for advice on drafts of this paper.
© Crown copyright.
Contributors: MQ and EA had the original idea for the study and together with PB and JJ collated and checked all the data. The paper was written jointly by all four authors. All the directors of the cancer registries in England contributed data, and some commented on drafts of the paper. MQ is the guarantor.
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Footnotes |
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Funding: None.
Competing interests: None declared.
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References |
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overview.
In:
Muñoz N,
Bosch FX,
Shah KV,
Meheus A,
eds.
The epidemiology of human papillomavirus and cervical cancer.
Lyons: International Agency for Research on Cancer, 1992:3-23. (IARC scientific publication No 119.)
registrations, England and Wales, 1971 to 1992.
London: HMSO
, 1979-98(Series MB1 Nos 1, 2, 4, 5, 7, 8, 10-16, 18-25.)(Accepted 19 January 1999)
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Israeli students are refusing to perform intimate examinations on anaesthetised women without their informed consent.