A study conducted by researchers at Oxford Population Health has found that women who are diagnosed with early stage breast cancer today are 66% less likely to die from the disease within five years of diagnosis than they were 20 years ago. The study was jointly funded by Cancer Research UK, the NIHR Oxford Biomedical Research Centre, and the University of Oxford. It is published in The BMJ.

Previous studies have shown that the risk of death after being diagnosed with early invasive breast cancer has decreased over the past few decades. This is the first study to identify the extent of the decreased risk and to analyse whether or not the decrease in risk applied to all patients or only to patients with certain characteristics for example, age, whether the cancer was detected by screening, involvement of lymph nodes, and tumour size and grade.

The results of this observational study can also help clinicians to estimate prognosis for patients diagnosed with breast cancer today.

Key findings:

• The risk of death due to breast cancer for all women included in the study was highest during the five years after diagnosis and then declined.
• For women diagnosed with early invasive breast cancer during the 1990s, the risk of death within five years of diagnosis was 14% on average. For women diagnosed during 2010-15, it was 5% on average.
• Improvements in prognosis applied to nearly all groups of women.
• Considering just the 156,338 women with a diagnosis during 2010-15, cumulative five year breast cancer mortality risk varied substantially between women with different characteristics.
• For most women diagnosed with breast cancer today, the 5-year risk of breast cancer death is likely to be less than 3% (ie less than 3 in 100).

Carolyn Taylor, Professor of Oncology at Oxford Population Health and lead author of the study, said: ‘Our study is good news for the overwhelming majority of women diagnosed with early breast cancer today because their prognosis has improved so much. Their risk of dying from their breast cancer in the first five years after diagnosis is now 5% on average.

‘Our study can also be used to estimate risk for individual women in the clinic. It shows that prognosis after a diagnosis of early breast cancer varies widely. Patients and clinicians can use our results to estimate prognosis moving forward. In the future further research may be able to reduce the risk of dying from breast cancer even more.’

The researchers analysed routinely collected data from the National Cancer Registration and Analysis Service on 512,447 women who were diagnosed with early breast cancer in England between January 1993 and December 2015. The women were followed until December 2020. This study focused on women who were initially treated with surgery. It did not include women who received treatment to reduce the size of their cancer before they had surgery, women whose cancer had already spread, or women diagnosed with more than one cancer. This study provides a detailed and accurate picture of breast cancer mortality in a complete population of women with early breast cancer for up to 20 years.

The study was supported by two patient representatives who are long-term survivors of breast cancer. They provided feedback on the study’s research question, helped to identify the analyses that would be most beneficial to patients, and provided input into the interpretation of the results and the final paper.

The paper, ‘Breast cancer mortality in 500 000 women with early invasive breast cancer in England, 1993-2015: population based observational cohort study‘, can be read in The BMJ.