Abstract
The optimal frequency of breast cancer screening has been a subject of debate since
the inception of the UK National Breast Screening Programme (NHSBSP). This paper reports
on the only randomised trial directly comparing different screening intervals. 99 389
women aged 50–62 years who had been invited to a prevalent screen were randomly allocated
after the scheduled prevalent screen date to the study arm (invited to three further
annual screens), or to the control arm (invited to the standard single screen 3 years
later). 37 530 women in the study arm and 38 492 in the control arm had attended the
prevalent screen. The endpoint was predicted breast cancer deaths. The prediction
was based on both the Nottingham Prognostic Index (NPI) and a similar method derived
from survival data from a series of tumours in the Swedish Two-County screening trial
(2CS). Both indices were based on the size, lymph node status and histological grade
of the invasive tumours diagnosed in the two arms of the trial. The pathology of the
cases diagnosed was subject to review by two pathologists using standard criteria.
The tumours diagnosed in the study arm were significantly smaller than those diagnosed
in the control arm (P=0.05). The relative risk of death from breast cancer for the annual compared with
the 3-yearly group was 0.95 (95% Confidence Interval (CI): 0.83–1.07, P=0.4) using the NPI and 0.89 (95% CI: 0.77–1.03, P=0.09) using the 2CS. Shortening of the screening interval in this age group is predicted
to have a relatively small effect on breast cancer mortality. Improvements to the
screening programme would be targeted more productively on areas other than the screening
interval, such as improving the screening quality.
Keywords
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Article info
Publication history
Accepted:
October 23,
2001
Received:
October 23,
2001
Identification
Copyright
© 2002 Published by Elsevier Inc.