Invasive breast cancer and breast cancer mortality after DCIS in women attending for breast screening in England
This research, undertaken by researchers at the University of Oxford, used data made available via the Office for National Statistics (ONS) Secure Research Service (SRS), which is being expanded and improved with ADR UK funding.
DCIS, or ductal carcinoma in situ, refer to cancerous cells in the ducts of the breast that haven’t spread to surrounding breast tissue and are therefore considered a form of non-invasive or pre-invasive breast cancer. The incidence and detection of DCIS has increased substantially in recent years, especially following the introduction of breast screening programmes, and it now accounts for approximately one fifth of all new diagnoses of screen-detected breast cancer. However, the long-term risks of invasive breast cancer (IBC) and breast cancer death after surgery for screen-detected DCIS are uncertain. Most women with DCIS are treated with surgery, often followed with radiotherapy.
To provide further information on the long-term consequences of DCIS, this research did a population-based study characterising the risks of IBC and death from breast cancer among all women diagnosed as having DCIS detected by screening in England. University of Oxford researchers led by Dr Gurdeep S. Mannu analysed data from 35,024 women in England diagnosed as having DCIS by the NHS Breast Screening Programme from its start in 1988 until March 2014. They compared rates of invasive breast cancer and of death from breast cancer with the corresponding national rates for women of the same age in the same calendar year.
The women with DCIS detected by screening had rates of both invasive breast cancer and death from breast cancer that, from a few years after diagnosis of DCIS, were more than double those of the general population, and the increases lasted until at least 20 years after diagnosis.
The study found higher 15-year cumulative rates of ipsilateral invasive breast cancer among women with low/intermediate grade tumours compared with high grade tumours. This may reflect a continuing risk of progression in low/intermediate grade tumours, as has been reported previously, or it might reflect under-treatment of these women, as most of them received breast conserving surgery with no record of radiotherapy. In either case, it clearly shows the long-term malignant potential of low/intermediate grade tumours.
Currently, surveillance of women after a diagnosis of DCIS focuses solely on the first few years. In the UK, for example, most women are recalled for yearly surveillance mammograms for five years, after which further follow-up is every three years via the national screening programme up to age 70 years. The research provides evidence of the long-term nature of the risk of invasive disease after a diagnosis of DCIS, even for women with low or intermediate grade disease.
This research is expected to have important implications on surveillance policy and on national (and potentially international) guidelines regarding the frequency and duration of post-diagnosis screening mammography for women with DCIS. Further studies are needed to build on these findings, in particular to try to work out which type of DCIS is most closely linked to the development of invasive breast cancer. This may, in turn, have further implications for follow-up and the frequency of surveillance imaging.
This research was the winner of the ONS Research Excellence Award 2020.