Effectiveness of cervical screening with age: population based case-control study of prospectively recorded data
BMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b2968 (Published 29 July 2009) Cite this as: BMJ 2009;339:b2968
All rapid responses
Sasieni et al (1) present a comprehensive and important study of
effectiveness of the UK cervical screening programme. One of their
findings is that cervical screening in women aged 20-24 has little or no
impact on rates of invasive cervical cancer up to age 30. They also
conclude that some uncertainty still exists regarding the impact of
screening on advanced stage tumours in women under age 30. The authors
refer to the Swedish nationwide audit (2) discussing our findings that
screening was equally effective for women at ages 23-29 and also effective
for non-squamous cervical cancer (1,3,4). We would like to take the
opportunity to comment on these issues.
Protection against cervical cancer can be demonstrated among women
under the age of 30 in the Swedish audit even when screen detected cancers
are excluded (OR 0.49 CI 0.24-0.98). We also analysed stage IB+ cervical
cancers in young women separately, as suggested by Cuzick (4) showing that
women at ages 27-29 were protected by screening (OR 0.36, CI 0.13-0.99) in
the previous three years, while this was not the case for women at ages 23
-26 (OR 1.09, CI 0.32-3.68). Further analyses of our data (all ages
combined) also show protection against Stage IB+ adenocarcinomas (OR 0.64
CI 0.45-0.91), and small cell carcinomas (OR 0.33, CI 0.12-0.91) (both
groups excluding adenosquamous carcinomas). However, if we apply a six
year screening interval in the Swedish audit (1, Appendix II) there is no
statistically significant protection of stage IB+ cervical cancer for
women aged 27-29 years (OR 0.69, CI 0.22-2.15), nor against stage IB+
adenocarcinoma for women of all ages (OR 0.72 CI 0.47-1.11).
We believe the reason for the difference in conclusions in Sasieni et
al (1,3) and the Swedish audit (2) regarding the screening effect for
young women, and for adenocarcinomas, is mainly a matter of definition of
who should be considered as sufficiently screened. The Swedish audit
evaluated the effectiveness of cervical screening according to the
intervals and age limits used in the Swedish cervical screening programme,
i.e. three years for ages 23-50 and then five years up to the age of 60,
whereas Sasieni et al (1) define a woman with a smear taken within six
years as sufficiently screened. To us, such an interval is seemingly too
long to protect women under the age of 30, or to protect against
adenocarcinoma of the cervix, while adherence to three yearly screening
gives a better protection against cervical cancers, at least from age of
27 (it should be noted that the pap smear may be taken up to three years
before this age).
Furthermore, screening detection of cervical cancer is not necessarily a
failure of the programme itself, since most of these cases are found at an
early FIGO stage with excellent prognosis and allowing fertility sparing
therapy. We agree with Sasieni et al that there is currently no evidence
to support screening under the age of 25, but women age 27 and up have a
benefit from having participated in three yearly screening. We therefore
advocate continued participation to cervical screening also for women at
ages 25 to 29 years.
References
1. Sasieni P, Castanon A, and Cuzick J. Effectiveness of cervical
screening with age: population based case-control study of prospectively
recorded data BMJ 2009;339:b2968, (Published 28 July 2009)
2. Andrae B, Kemetli L, Sparen P, et al. Screening-preventable
cervical cancer risks: Evidence from a nationwide audit in Sweden. J Natl
Cancer Inst 2008;100:622–629
3. Sasieni P, Castanon A, Cuzick J. Screening and adenocarcinoma of
the cervix. Int J Cancer. 2009;125(3):525-529.
4. Cuzick J, Routine Audit of Large-Scale Cervical Cancer Screening
Programs. Editorial. J Natl Cancer Inst 2008;100:605–606.
Competing interests:
None declared
Competing interests: No competing interests
Cervical cancer is of two types: adeno and squamous. Adenocarcinoma
is only 20% and occurs at an early age mostly. Squamous cell carcinoma occurs at
older ages. Screenig of the cervix cannot prevent total
incidence but it can detect the changes 8-10 yrs early at pre cancerous
state and pt can plan early for treatment. With minor procedures cancer
occurrence can be prevented. The mortality, morbidity and treatment cost
due to cancer can be reduced markedly if precancer/cancer is detected
early by screening procedures between ages 15-60 (sexually active} but
adenocarcinoma incidence may not come down. With PAP smear cervical screening,
squamous cell cancer/precancer can be detected early. Hence its incidence in old age can
be markedly decreased.
Competing interests:
Effectiveness of cervical screening with age
Competing interests: No competing interests
The benefits of screening women age 20-24
The danger of Sasieni and colleagues’ recent paper[1] is that it will
be used as evidence justifying not screening women under age 25 years,
especially since their summary answer states ‘cervical screening has no
effect at ages 20-24.’
Reading the full paper on line reveals the possibility of alternative
conclusions: ‘our data do not rule out the possibility of screening women
aged 20-24 being effective in reducing stage 1b+ invasive cancer…..’
Indeed, other studies show screening women less than 25 years reduces
invasive cancer by half [2], [3]
There is no doubt screening women under 25 years is less effective
than for older women but much of this is due to the lack of a protective
effect conferred by a screening history; the sensitivity of a first
cervical smear being only around 50%. Delaying acquisition of a screening
history will sadly, carry a very heavy price for some. Failing to screen
from age 20 is a lost opportunity to engage young women and establish
routine screening. This is already happening in the UK where coverage
rates for women aged 25-29 are falling in England compared to Wales, where
screening still commences from age 20 (data from Wales and England’s
cervical screening programmes)[4], [5].
Sasieni et al allude to the harms of treatment following screening.
As concluded in a recent review by Prendiville, the evidence suggests that
there is no significant adverse pregnancy outcome following treatment by
large loop excision of the transformation zone (LLETZ)[6]. Adverse
neonatal outcome was shown following cone biopsy, but this would be an
unusual treatment in young women.
The oft quoted psychological morbidity of screening has not been
compared with the psychological morbidity of not being able to access
screening for women concerned about their risk of cervical cancer, to
which we can attest as clinicians.
The full paper makes for difficult reading where definitions are
unclear and at worst incorrect. Case selection is not explained, for
example how were the 38 cases of cervical cancer from Wales selected in
1990-2? The paper demonstrates once again that you can ‘prove’ virtually
anything with statistics, whilst one is left with the feeling that the
human condition and benevolence requires more complex investigation and
understanding. In the meantime, we agree that “women need to be aware of
the common negative consequences of regular screening, but they should
perhaps think of it as a costly and imperfect insurance policy that may
save them from the horrors of invasive cervical cancer.” [7]
Alison Fiander
Amanda Tristram
1. Sasieni, P., A. Castanon, and J. Cuzick, Effectiveness of cervical
screening with age: population based case-control study of prospectively
recorded data. BMJ, 2009. 339: p. b2968.
2. Rieck, G.C., et al., Cervical screening in 20-24-year olds. J Med
Screen, 2006. 13(2): p. 64-71.
3. Andrae, B., et al., Screening-preventable cervical cancer risks:
evidence from a nationwide audit in Sweden. J Natl Cancer Inst, 2008.
100(9): p. 622-9.
4. Cervical Screening Wales, KC53/61/65 Statistical Report – Adroddiad
Ystadegol 2007/08. 2008.
5. Cervical Screening Programme. 2007/8 Data Tables. 2008; Available
from: http://www.ic.nhs.uk/statistics-and-data-
collections/screening/cervical-cancer/cervical-screening-programme-2007-08
-%5Bns%5D.
6. Prendiville, W., The treatment of CIN: what are the risks?
Cytopathology, 2009. 20(3): p. 145-53.
7. Sasieni, P.D., Outcomes of screening to prevent cancer: think of
screening as insurance. BMJ, 2003. 327(7405): p. 50.
Competing interests:
None declared
Competing interests: No competing interests