Ductal carcinoma in situ, or DCIS, is called stage 0 or non-invasive breast cancer.

With DCIS, the abnormal cells are contained inside the milk ducts. The term “in situ” means “in place” because the abnormal cells have not spread into nearby breast tissue.

Surgery is the first step in treating DCIS. Depending on how much of the breast is affected, surgery can be a mastectomy or a lumpectomy. If a large part of the breast is affected, a total mastectomy will be recommended. If the spread within the milk ducts is limited, you’ll likely have a choice between a mastectomy and a lumpectomy.

The good news is that overall survival is the same for women with DCIS who have a mastectomy and those who have a lumpectomy, with or without radiation therapy. This means both treatments lower the risk of dying from breast cancer or another cause by the same amount.

Women who have a mastectomy for DCIS generally don’t usually need radiation therapy. However, in rare cases, it may be recommended because of the amount of DCIS in the milk ducts or the location of it.

A lumpectomy for DCIS is usually followed by radiation therapy to the whole breast. This helps lower the chance of DCIS coming back or that invasive breast cancer will develop in the same breast. Survival for women with DCIS who have a lumpectomy is the same, whether or not they have radiation therapy. So, decisions about radiation therapy are now becoming more personalized.

When personalizing treatment for DCIS, doctors consider the tumor size and features that are seen under a microscope, including the tumor grade and how much tissue was removed around it, which is called a margin. They also consider a woman’s age and personal preferences.

Hormone therapy isn’t usually recommended for women with hormone receptor-positive DCIS who have a mastectomy. This is because there’s a very low risk of the cancer coming back or invasive breast cancer developing in the opposite breast. The benefit of hormone therapy would likely be very small and would mostly affect the risk of cancer in the opposite breast.

The National Comprehensive Cancer Network, or NCCN, recommends women who are treated with a lumpectomy for hormone receptor-positive DCIS consider taking hormone therapy, either tamoxifen or an aromatase inhibitor, for 5 years. In these instances, hormone therapy lowers the risk of a DCIS recurrence and the chance of invasive breast cancer developing in both the treated breast and opposite breast.

Chemotherapy and other drug therapies typically used for invasive breast cancer are not used to treat DCIS.

For more information, visit the Treatment for DCIS page on komen.org. There you’ll find details about treatment, along with helpful topics like questions to ask your health care provider about the diagnosis, treatment and follow-up care.