by Stephen W Duffy, Daniel Vulkan, Howard Cuckle, Dharmishta
Parmar, Shama Sheikh, Robert A Smith, Andrew Evans, Oleg Blyuss, Louise Johns,
Ian O Ellis, Jonathan Myles, Peter D Sasieni, Sue M Moss
The Lancet
Oncology: VOLUME 21,
ISSUE 9, P1165-1172, SEPTEMBER 01, 2020
Background
The appropriate age range for breast cancer screening
remains a matter of debate. We aimed to estimate the effect of mammographic
screening at ages 40–48 years on breast cancer mortality.
Methods
We did a randomised, controlled trial involving 23 breast screening
units across Great Britain. We randomly assigned women aged 39–41 years, using
individual randomisation, stratified by general practice, in a 1:2 ratio, to
yearly mammographic screening from the year of inclusion in the trial up to and
including the calendar year that they reached age 48 years (intervention
group), or to standard care of no screening until the invitation to their first
National Health Service Breast Screening Programme (NHSBSP) screen at
approximately age 50 years (control group). Women in the intervention group
were recruited by postal invitation. Women in the control group were unaware of
the study. The primary endpoint was mortality from breast cancers (with breast
cancer coded as the underlying cause of death) diagnosed during the
intervention period, before the participant's first NHSBSP screen. To study the
timing of the mortality effect, we analysed the results in different follow-up
periods. Women were included in the primary comparison regardless of compliance
with randomisation status (intention-to-treat analysis). This Article reports
on long-term follow-up analysis. The trial is registered with the ISRCTN
registry, ISRCTN24647151.
Findings
160 921 women were recruited between Oct 14, 1990, and Sept
24, 1997. 53 883 women (33·5%) were randomly assigned to the intervention group
and 106 953 (66·5%) to the control group. Between randomisation and Feb 28,
2017, women were followed up for a median of 22·8 years (IQR 21·8–24·0). We
observed a significant reduction in breast cancer mortality at 10 years of
follow-up, with 83 breast cancer deaths in the intervention group versus 219 in
the control group (relative rate [RR] 0·75 [95% CI 0·58–0·97]; p=0·029). No
significant reduction was observed thereafter, with 126 deaths versus 255 deaths
occurring after more than 10 years of follow-up (RR 0·98 [0·79–1·22]; p=0·86).
Interpretation
Yearly mammography before age 50 years, commencing at age 40
or 41 years, was associated with a relative reduction in breast cancer
mortality, which was attenuated after 10 years, although the absolute reduction
remained constant. Reducing the lower age limit for screening from 50 to 40
years could potentially reduce breast cancer mortality.
Funding
National Institute for Health Research Health Technology Assessment
programme.
https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(20)30528-3/fulltext?rss=yes#section-7c530872-6235-4433-899c-b3f276970189 (as of 24.11.2020)
