The deaths prevented were all women in their 40s, but even with almost 25 years of follow-up, there is no suggestion that screening only postponed these deaths – these women really do appear to have been cured. The benefit is mostly seen in the first ten years, but the reduction of mortality persists in the long term.
Professor Peter Sasieni, School of Cancer & Pharmaceutical Sciences
14 August 2020
Breast screening women in their forties saves lives
A new study has demonstrated that offering annual screening by mammography from age 40 results in fewer women dying from breast cancer than screening from age 50.
The UK has a breast cancer screening programme offering mammography to women aged 50-70, every three years. However, there continues to be uncertainty over whether to offer screening at a younger age, including whether this can lead to overdiagnosis.
A new study funded by the National Institute for Health Research Health Technology Assessment Programme, involving Professor Peter Sasieni from the School of Cancer & Pharmaceutical Sciences at King’s and led by Queen Mary University of London, has found that breast screening women aged 40-49 reduces breast cancer mortality, with minimal increased overdiagnosis.
Between 1990 and 1997, the UK Breast Screening Age Trial randomised more than 160,000 women aged 39-42, to receive either annual mammography or the usual NHS Breast Screening Programme, which usually commences at age 50. The women were followed for an average of 23 years to learn the risks and benefits of inviting women of this age group for additional screening.
This study, published in Lancet Oncology presents the follow-up results of the trial and shows that among women screened regularly, screening reduced their chances of dying from breast cancer within the first 10 years by approximately a third. In absolute terms, about one woman avoided dying in her forties or early fifties for every 1,000 screened. On average, those women are estimated to live for an extra 35 years.
The results also show only a modest amount of overdiagnosis of women in their forties, but this excess disappeared once women were invited for routine breast screening at age 50, suggesting that beginning the programme earlier does not increase a woman’s chance of being overdiagnosed.
Particularly with the disruption caused in cancer settings by the current pandemic, the research underlies the importance of detecting cancer early when it can be treated with fewer side-effects and more successfully.
In order to meet the NHS plan to diagnose three-quarters of cancer early by 2028, the government should consider extending breast cancer screening to start at age 45 so that women would be guaranteed to receive their first invitation before the age of 48. Not all women want to have breast screening, but, given these results, others would choose to be screened.
Professor Peter Sasieni, School of Cancer & Pharmaceutical Sciences
However, not only is mammography expensive for the NHS, but there are downsides in participating in screening. Further research is needed to clarify whether progress in early detection technology and treatment of breast cancer since the start of the trial may modify the screening-related reduction in mortality in the 40-49 age group. It should also be noted that consideration to the cost-effectiveness of lowering the screening age was not given.
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Academic Director of King's Clinical Trials Unit