PUBLISHED ON: 27 February 2021

Ductal carcinoma in situ (DCIS) is an early form of breast cancer. In the UK, 7,000 people are diagnosed with DCIS every year. Treatment is recommended for all these people to reduce the chance of DCIS becoming invasive breast cancer. But there are still unanswered questions regarding it. Answering them through research would mean tailored DCIS treatment, ensuring the best possible quality of life for people diagnosed with it.

What is DCIS?

DCIS is a non-invasive form of breast cancer. At this point, cancer cells haven't spread into surrounding breast tissue or to other parts of the body. But, if left untreated, it can sometimes gain the ability to spread and turn into invasive breast cancer.

A diagram showing what DCIS looks like on a cellular level

It is thought that around half of DCIS cases will never cause harm during a person’s lifetime, because it won’t develop the ability to spread or will grow incredibly slowly. People with this kind of DCIS could safely avoid treatment. But currently, there is no way to tell what kind of DCIS someone has and everyone is recommended treatment.

So what do we need to understand about DCIS to ensure everyone receives the most suitable treatment? And what research is happening right now?

How can we understand DCIS better?

Although the grade of the DCIS can help predict if it will become invasive, there is currently no way of knowing if this will happen. The main challenge researchers are trying to address is how cancer cells gain the ability to invade surrounding tissue.

There are several different theories about how DCIS can turn into invasive breast cancer:

  • DCIS and invasive breast cancer arise independently from different cells within or around the tumour.
  • Individual DCIS cells in a tumour over time gain different genetic changes. A specific combination of these changes can give an ability to spread.
  • The ability to spread depends on the features a cell has. These features can arise in different ways and don’t always depend on specific changes in genes.
  • Invasive breast cancer doesn’t arise from a single cell. Multiple cells in a tumour with different genetic changes can escape the duct and become invasive.

Through studying these theories, researchers are trying to understand exactly how DCIS becomes invasive breast cancer. This knowledge could reveal what clues we need to look for in DCIS tumours to know if they can cause harm. Knowing this would help to ensure that people are offered the best treatment to prevent this from happening.

Researchers we fund are also working to expand our knowledge about DCIS and how we can identify DCIS that will not become invasive.

Appropriately treating high-risk DCIS

If we know that DCIS is likely to become invasive breast cancer, we need to make sure that treatment can stop it.

The usual treatment for DCIS limited to a small area is breast-conserving surgery, which removes only the affected area of the breast. Whole breast radiotherapy is then given to people who have a higher chance of DCIS returning. This radiotherapy is given to make sure the DCIS doesn’t come back and progress to invasive breast cancer.

Professor Ian Kunkler, based at the University of Edinburgh, is working to understand if an additional dose of radiotherapy to the area where DCIS has been removed could reduce the chance of it coming back.

How can we treat DCIS that is less likely to cause harm?

If all cases of DCIS don’t need intensive treatment, how can we find the most appropriate treatment – reducing the risk of DCIS causing harm, ensuring it doesn’t cause unnecessary worry and making sure treatment is still effective.

There are already clinical trials happening in the UK and elsewhere to find the most appropriate way to manage low-risk DCIS. The LORIS clinical trial, run by researchers at the University of Birmingham, is looking to assess whether active monitoring of women with low-risk (which means small and low-grade) DCIS could replace surgery. The active monitoring would include annual mammograms, with the aim of sparing people from potentially unnecessary surgery when their DCIS may never be life-threatening.

Ensuring open and informed communication about DCIS

The communication between healthcare professionals and people with DCIS is also essential. Without being able to reliably evaluate if DCIS will cause any harm, making treatment decisions is extremely difficult.

Tools that help better estimate risk of DCIS becoming invasive breast cancer would allow well-informed conversations between patients and their healthcare team, so that they can make decisions regarding treatment that best suits their needs.

Although DCIS has an excellent prognosis, it needs to be researched further if we are to find the best possible way to treat it, so that the treatment offers the best quality of life for those diagnosed with it.


We’re funding research that is doing just this as well as discovering how we can prevent breast cancer, save lives and live well with the disease.

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