Friday 15 September 2000
Researchers at The Institute of Cancer Research, in collaboration with the Office for National Statistics (ONS), have shown that mortality from breast cancer has substantially reduced since the introduction of the national breast cancer screening programme. The research was funded by the Department of Health.
Their study, published in tomorrow's BMJ1, assessed the impact of the NHS National Breast Screening Programme - introduced in England and Wales in 1988. The results of the research demonstrate that the screening programme, together with improved treatment and early presentation due to greater breast cancer awareness, has lowered mortality rates from breast cancer in the 55-69 year age group by 21%.
It is estimated that, of this fall, 6-7% was a direct effect of screening - correlating to over 300 deaths prevented per year among women in the age group 55-69 years. The remaining 15% drop in mortality (over 650 lives saved) is due to other factors including improvements in treatment with tamoxifen and chemotherapy and improved awareness of breast cancer, leading to women presenting with the disease earlier.
Dr Roger Blanks an epidemiologist at The Institute of Cancer Research and first author of the study said:
"We are now beginning to see the positive effect of screening on breast cancer death rates and are predicting that screening, treatment improvements and changes in underlying risk will continue to decrease mortality in women aged 55-69 over the next ten years. "
In England and Wales women aged 50-64 years are invited for breast screening every three years. Screening allows doctors to detect cancers at an early stage, when treatment is most effective.
The NHS Breast Screening Programme was introduced in 1988 on the recommendation of the Forrest committee2, after it was found that mammography could reduce mortality from breast cancer in women over 50 by 25-30%, over a 10 year period.
This reduction was predicted on the basis of detection rates observed in a previous two-county trial. Importantly, in this study by Swedish researchers, all deaths from women who had been diagnosed with breast cancer before the start of the trial were excluded from the analysis.
Various factors explain why the UK screening programme has not yet led to the predicted 25% reduction in mortality.
In contrast to the Swedish study, the national mortality statistics in the UK study include women who already had breast cancer at the time of their first invitation to screening - many deaths from breast cancer in the 1990s occurred in women diagnosed with breast cancer before their first mammogram. This factor diluted the effect that screening could be shown to have on mortality rates.
In addition, although the screening programme officially started in 1988, it was not until 1995 that all eligible women in England and Wales were invited for screening. Areas not included in the screening programme until 1995 could not be expected to show any effect of screening until at least 1999.
At the start of the UK's national programme, the sensitivity of mammograms used for detecting breast cancer was lower than that in the Swedish study. This lower sensitivity in the early years affected the number of lives saved in the 10 year study period. However, improvements in screening techniques introduced since 1995 have resulted in higher detection rates.
Dr Blanks commented: "The combination of all these factors suggest that it is too early to expect the programme to demonstrate a reduction in mortality of 25%. We should see the full effects of the screening programme over the next ten years, with a large effect from 2000 - 2005."
Dr Peter Rigby, Chief Executive of The Institute of Cancer Research commented: " Any reduction in the number of women dying from breast cancer is good news. An effective screening programme means that the disease will be detected earlier, and earlier detection means that treatment will work much better."
The study used national data on breast cancer deaths for 1971-89 to predict the number of deaths for 1990-8. The effect of screening and other factors on breast cancer deaths during this period was then estimated by comparing observed deaths with those predicted among women aged 50-79, some of whom were affected by screening and treatment, and some by treatment only.
1. Effect of NHS breast cancer screening programme on mortality from breast cancer in England and Wales, 1990-8: comparison of observed with predicted mortality. BMJ Volume 321.
2. Forrest APM. Breast cancer screening: report to the health ministers of England, Wales, Scotland and Northern Ireland: HMSO 1986.
For more information, please contact the Institute of Cancer Research press office on:-
Tel: 0207 970 6030
email: [email protected]
Notes to Editors
- Research was conducted at The Institute of Cancer Research's Cancer Screening Evaluation Unit. The Unit monitors the national breast and cervical cancer screening programmes. The research was conducted in collaboration with the National Cancer Intelligence Centre at the ONS.
- The sensitivity of mammography techniques has improved in the last five years - changes have included refinements to film-density and the introduction of a 'two-view' procedure at first screening.
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