Ductal Carcinoma In Situ (DCIS) data story

There are two main types of breast cancer:

• non-invasive (when the cancer is not yet showing any signs of spreading)
• invasive (when the cancer has spread outside of the milk ducts into the surrounding breast tissue)

DCIS is a disease where cancer cells are found in the milk ducts. ‘In situ’ means that the cancer cells have not spread from the milk ducts, and so DCIS is a non invasive cancer. However, the cancer cells can change and start to spread.

Many women with DCIS have no symptoms. Therefore, the number of women diagnosed with DCIS increased dramatically after the introduction of breast screening programmes. Today, 1 in 5 new diagnoses of breast cancer found through screening are DCIS.

Most women diagnosed with DCIS are treated with surgery to the breast. Some women also receive radiotherapy or hormone treatment.

In March 2020, the researchers published a study on the long-term risks of DCIS. They used data on women diagnosed with the disease via the breast screening programme from 1988 to 2014.

The research findings showed that these women have a higher risk of developing invasive breast cancer and of dying from breast cancer when compared to the general population.

In this study, around 9 out of 1000 women diagnosed with DCIS developed invasive breast cancer each year.

In the same group, around 1 out of 1000 women died from breast cancer each year. This was more than expected when compared to the general population.

The likelihood of developing invasive breast cancer and dying from breast cancer continued to increase for at least 20 years after diagnoses of screen detected DCIS.

The study results also suggested that women who had more extensive surgery, such as a mastectomy, had a lower long-term risk of invasive breast cancer. A mastectomy is an operation to remove a breast. This is compared to women who had breast conserving surgery, even when radiotherapy was given. Breast conserving surgery removes the cancer cells while keeping as much of the breast tissue and shape as possible.

The long term risks of DCIS were unclear.

At the time of the study, one of the researchers was training to be a breast surgeon. While working in a breast clinic, he met a woman with DCIS who asked about the long term risks following her diagnosis. He realised that little was known about this, even though around 7,000 women are diagnosed with DCIS each year.

After treatment for DCIS, women are currently monitored closely in the first few years. In the UK, women are called for a mammogram every year for 5 years. A mammogram is an X-ray picture of the breast used to spot early signs of breast cancer. After 5 years, these women are not monitored as closely. The research shows long-term risks of DCIS beyond the first 5 years.

The research results are expected to inform guidelines on how often and for how long women should be offered mammograms after a DCIS diagnosis. In the meantime, women should regularly check their breasts. Find out more about checking your breasts here.

The researchers are also working on other projects in relation to DCIS.

They are examining the long term outcomes of women who were diagnosed with DCIS outside of the breast screening programme. This includes women who were diagnosed after going to their GP with breast cancer symptoms, or through A&E. Women who referred themselves directly to the screening service are not included.

They are also developing a system to identify women who developed invasive breast cancer following treatment in England. From this, researchers and policy makers can explore ways to improve outcomes of women with breast cancer in the future.

The researchers are also looking into biomarkers for breast cancer. Biomarkers indicate that there may be cancer. The team are carrying out a large study of trends in breast cancer deaths in England.

The researchers used NCRAS data to look at the long term risks of DCIS.

NCRAS has legal permission to collect patient-level data and to use it to protect the health of the population. This permission was granted to NCRAS under Section 251 of the NHS Act 2006, whilst it was still part of Public Health England (PHE). Everyone working with patient data is trained in information governance and follows strict rules to make sure patient information stays safe. You can click here to read more about how we keep data safe. Only anonymous data was used for this work.

For this project they used data from the Cancer Analysis System (CAS). CAS holds many data sets on cancer. The CAS data was combined with data from the NHS breast screening audit.

For ongoing work, the team are also using the other following data sets:

• Radiotherapy Data Set (RTDS)
• Cancer Waiting Times (CWT) data set
• Hospital Episode Statistics (HES) data set

The results from the study were shared at the Public Health England Cancer Outcomes conference. Representatives from patient groups attend this conference and provide comments.

Patient representatives from the Independent Cancer Patients’ Voice (ICPV) are involved in ongoing work. They guide the research direction by highlighting the questions that need to be answered.

NCRAS have also worked with ‘use MY data’ to produce this data story. ‘use MY data’ is an independent patient movement focused on promoting the benefits of using patient data to save lives and improve outcomes. We are inviting a patient member of ‘use MY data’ to comment on each data story.