Articles16-year mortality from breast cancer in the UK Trial of Earaly Detection of Breast Cancer
Introduction
The efficacy of screening for breast cancer by mammography in women aged 50 years and older is now well established from the results of several randomised trials, and several countries have implemented or are planning nationwide screening programmes. However, despite further analyses, the efficacy of screening of women aged younger than 50 years continues to be the subject of considerable debate.
The UK Trial of Early Detection of Breast Cancer (TEDBC) was set up in 1979 to investigate the effect on breast-cancer mortality of both screening (by mammography and clinical examination) and an education programme in breast self-examination.1 TEDBC was non-randomised, and designed to compare eight geographically separate districts in England and Scotland. After a mean 6·6 years of follow-up, breast-cancer mortality was 14% lower in the two populations offered screening than in the comparison populations, the difference increasing to 20% when differences in pretrial mortality were taken into account (p=0·06).2 After 10 years of follow-up, this difference remained similar (p=0·01), with no difference from the comparison centres observed in the two breast self-examination centres combined, despite a significant difference between the two.3
In common with most randomised trials, TEDBC was not designed to study the effect of screening in specific age-groups. However, meta-analyses of randomised trials have been used to argue for and against the existence of an effect of mammography in women younger than 50 years.4, 5 The 10-year analysis of TEDBC showed no significant difference between the effect of screening in women aged 45–49 years at entry and that in older women.3 For a further 4–6 years the intervention centres in TEDBC continued to recruit additional women into the study as they reached 45 years, giving a large population in this age-group. We report the mortality results up to 16 years of follow-up and look in more detail at the effect of screening according to age at entry.
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Study design
The details of the trial are described elsewhere.1 The two screening centres, Guildford and Edinburgh, invited women aged 45–64 years to screening sessions every year for 7 years, with screening by mammography and clinical examination every 2 years and by clinical examination only in the intervening years. The two breast self-examination centres, Huddersfield and Nottingham, offered women in the same age-range an invitation to attend an education session on breast self-examination on entry to
Results
Table 2 shows the numbers of women attending their first screening session and the average number of screenings per woman invited by age at entry in cohorts 1 and 2–7. Attendance at first screening was 60% in Edinburgh and 72% in Guildford and fell slightly with increasing age. Not all women invited for screening in each year were invited at subsequent rounds, because some moved away from the district or died. Attendance at subsequent screenings also varied according to the protocol for
Discussion
These results show the long-term effect of screening in TEDBC: in women in the initial cohort breast-cancer mortality was 27% lower in the screening centres than in the comparison districts at 16 years of follow-up. Cumulative mortality in the screening and comparison centres continued to diverge up to 16 years of follow-up.
Follow-up of this study to the end of 1995 meant that several years were included during which the UK NHS breast-screening programme, introduced over a 5-year period from
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