DCIS and the risk of invasive breast cancer

DCIS is a form of pre-cancer. The purpose of treatment for DCIS is to lower the risk it will develop into invasive cancer.

In some cases, DCIS will never develop further or will grow so slowly that it would never cause harm during a person’s lifetime. Other times it will.

At the moment, it is impossible to accurately predict who with DCIS will develop invasive breast cancer in the future. DCIS that is not treated is more likely to become invasive breast cancer. Read about Treatment for DCIS.

What doctors consider

To understand whether DCIS has a higher or lower chance of becoming invasive, doctors look at:

• the grade and features of DCIS (we explain these in How DCIS develops in the breast)
• characteristics of the individual patient, such as family history of breast cancer.

These factors influence the treatment options.

You can be treated successfully for DCIS. Ten years after treatment is complete, survival rates are more than 98%.

Factors that indicate a higher risk of invasive breast cancer after DCIS

After treatment for DCIS, the risk of it becoming invasive breast cancer may be higher in people who:

• are younger (under 40 years of age) at diagnosis of DCIS
• have a large area of DCIS (e.g. greater than 4cm)
• have high-grade (fast-growing) DCIS or a pathological change called ‘comedo necrosis’
• have abnormal cells at the edge of the tissue removed during surgery (known as ‘close’, ‘involved’ or ‘positive’ margins)
• have DCIS in more than one area of the breast (called multifocal disease)
• have a family history of breast cancer.

Treatment for DCIS is recommended in order to minimise the chance of DCIS coming back and of developing invasive breast cancer.

Factors that indicate a lower risk of invasive breast cancer after DCIS

The risk of invasive breast cancer may be lower in people who:

• are older at diagnosis of DCIS (over 60 years of age)
• have only a small area of DCIS (e.g. less than 1.5 cm)
• have low or intermediate grade DCIS, which grows slowly
• have clear margins. This means the DCIS is removed along with enough healthy tissue around it to ensure that all DCIS has been completely removed)
• have no evidence of cancer cells at the edge of the tissue removed during surgery (known as ‘clear margins’).
• have DCIS in only one area of the breast.

Find out about Treatment for DCIS.

The risk of invasive breast cancer when DCIS is not treated

DCIS that is ‘high-grade’ (Grade III) and not treated is more likely to become invasive breast cancer than low-grade DCIS.

The time it takes to progress varies and it is impossible to predict accurately. However, the average for untreated DCIS to develop into invasive breast cancer may be:

• around 5 years or less for high-grade (Grade III) DCIS
• 15 years or more for low-grade (Grade I) DCIS

When you have high-grade DCIS, it is possible you already have invasive breast cancer present as well.

Studies have shown that DCIS is usually (not always) in a single area of the breast. In most cases, if invasive breast cancer develops, it in the same area as the original DCIS.

This information has been an important finding to confirm that DCIS can progress to invasive breast cancer and also important in working out how to manage DCIS surgically.