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TVCS scientific
meeting and AGM, 15 February 2001, at University College, London
Dr Amanda
Herbert from St. Thomas's Hospital kindly agreed to come and
describe her recent work which attempted to address two criticisms
of cervical screening in general and the NHS Cervical Screening
Programme (NHSCSP) in particular - namely that cervical cancer is
a rare disease and too much effort and money is spent on screening
and that cervical screening has, in any case, been ineffective.
This involved examining data from the Office of National Statistics
(available on their website - http://www.statistics.gov.uk/) regarding
registration and incidence of invasive cervical cancer and carcinoma-in-situ
(CIS) by 5 year birth cohort and age at registration.
A brief history
of the introduction of cervical screening in the UK reiterated the
fact that it was introduced sporadically in a few centres in the
1950's, nationally in 1967, (via payments to GP's) and became more
widespread in the 1980's as Health Authorities introduced call and
recall systems. The NHSCSP was established in 1988. The figures
for the incidence of invasive cervical cancer show it to have declined
gradually until 1983, and then increased until around 1988, following
which there has been a sharp decline (so far 40% compared to 1988
levels). This has led to the conclusion that cervical screening
was ineffective before 1988. Furthermore, despite the demonstrable
improvement since 1988, criticism continues and staff morale, retention
and recruitment are increasingly difficult.
Firstly, the
figures for the registrations of cervical cancer and CIS were shown
in graphical form for the years 1971, 1981 and 1991. There was a
roughly 8-fold (700%) increase in CIS with time while the registrations
for invasive cancer had fallen only slightly (about 10%). There
had also, incidentally, been a shift in the age with most registrations
from the 30-34 to the 25-29 age group. This raised the question
of why, when so many more cases of CIS were being detected and treated,
was there so small an effect on the registrations of cervical cancer?
Examination
of 5-year birth cohorts (i.e. groups of women born within 5 years
of each other) showed that there was a marked increase in CIS, particularly,
and invasive carcinoma in the cohorts born from 1937 onwards which
was difficult to explain by increased rates of detection and seemed
to indicate a true increase in disease risk. By contrast, those
born in the 1920's and early 1930's appeared to have a genuinely
lower risk of disease.
Therefore, it
is possible to draw the conclusion that cervical cancer registrations
remained relatively static in the 1970's and most of the 1980's
because screening, though far from perfect, was preventing a significant
minority of cervical cancers in higher-risk women who had come of
age two decades previously, thus effectively cancelling out an increase.
Some estimates suggest that screening was preventing about 25% of
cancers in the mid-1980's. This contrasts with estimates around
80-90% today.
Dr Herbert has
contributed a great deal to the development and implementation of
cervical screening and is committed to and passionate about her
chosen field. It was a relief to hear a positive message delivered
with enthusiasm and gratifying, also, that these conclusions found
their way into the national press, subsequently.
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