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A new study has provided evidence that women who have been diagnosed with ductal carcinoma in situ (DCIS) outside the NHS breast screening programme are around four times as likely to develop invasive breast cancer and to die from breast cancer than women in the general population. The study is published in The BMJ.

DCIS is a pre-invasive breast cancer, meaning that the cancer is contained within the milk ducts inside the breast. DCIS is normally treated with surgery. If the cancer has spread beyond the milk ducts and into the surrounding breast tissue, it is called invasive breast cancer.

DCIS can be detected by the NHS breast screening programme, but some diagnoses occur outside the screening programme, either because women are not in the eligible 50-70 year age range, or they did not respond to a screening invitation, or because their DCIS developed between screens. Women who are diagnosed with DCIS in England are offered yearly mammograms for five years after their treatment, after which women aged 50-70 years continue to be invited to mammograms every three years as part of the NHS breast screening programme.

The researchers looked at data from all 27,543 women in England who were diagnosed with DCIS outside the NHS breast screening programme between 1990 and 2018. The researchers then looked at the women’s health records up to December 2018 to find out whether or not they went on to develop invasive breast cancer or had died from breast cancer. For women aged 50-64 years, the researchers also compared the results with women who had been diagnosed with DCIS through the NHS breast screening programme.

Key findings:

  • By December 2018, 3,651 women with non-screen detected DCIS had developed invasive breast cancer and 908 women had died from breast cancer;
  • Women with non-screen detected DCIS were around four times more likely to develop invasive breast cancer or to die from breast cancer when compared with women in the general population;
  • The increased risk of invasive breast cancer and of death from breast cancer both lasted for at least 25 years after diagnosis;
  • Treatment of DCIS with mastectomy was associated with a lower risk of invasive breast cancer when compared with treatment with breast-conserving surgery, but did not impact the risk of death from breast cancer.

Mr Gurdeep S. Mannu, Clinical Research Fellow in Cancer Surgery at Oxford Population Health and the Nuffield Department of Surgical Sciences who is lead author of the study, said ‘This is the first time that we have been able to evaluate the long-term outcomes in all women diagnosed with DCIS on a population level in England. We have provided evidence that the increased risk of invasive disease and breast cancer death following a diagnosis of DCIS in both screen detected and non-screen detected DCIS lasts for at least 25 years. These findings should inform considerations regarding the frequency and duration of surveillance following a diagnosis of DCIS, particularly for women diagnosed at younger ages.’

The researchers note that the findings presented in this study are observational and they did not have information to be able to account for additional risk factors, such as lifestyle choices, for developing breast cancer.

A linked editorial explores whether or not a more personalised risk-based approach might be possible, especially for younger women.

The study was funded by Cancer Research UK and the National Institute for Health and Care Research Oxford Biomedical Research Centre.