Stage 0 breast cancer, also known as ductal carcinoma in situ (DCIS), is a non-invasive cancer where abnormal cells have been found in the lining of the breast milk duct. In this stage, the atypical cells have not spread outside of the ducts or lobules into the surrounding breast tissue. DCIS is the most common form of non-invasive cancer. Stage 0 breast cancer is considered a very early cancer that is highly treatable, but if left untreated or undetected, it can spread into the surrounding breast tissue. Stage 0 breast cancer is not invasive, though it could be later. It’s less advanced than stage I cancer. There are two types of stage 0 breast cancer: noninvasive Paget’s disease, a rare form of breast cancer in the nipple, and DCIS.

Even though Stage 0 breast cancer is considered “non-invasive,” it does require treatment, typically surgery or radiation, or a combination of the two. Chemotherapy is usually not part of the treatment regimen for Stage 0 breast cancer. Because it’s not possible to predict whether a stage 0 breast cancer will invade the breast tissue around it, most people undergo treatment, which may include surgery, radiation therapy, and hormone therapies such as tamoxifen. If the abnormal cells are hormone receptor-positive, the next step may involve long-term treatment with a hormone-based drug.

It is important to note that opinions about the optimal treatment for DCIS vary widely among doctors. A new study from researchers at Columbia University Vagelos College of Physicians and Surgeons may help women and their physicians narrow down the treatment choices. “DCIS is considered a pre-invasive cancer, but the current standard of care is to treat it like an early-stage invasive breast cancer,” says Apar Gupta, MD, assistant professor of radiation oncology at Columbia University Vagelos College of Physicians and Surgeons and lead author of the study. It’s important to understand that radiation and hormone treatments do not change survival—the 10-year survival rate for women diagnosed with DCIS is 98% regardless of whether they receive either treatment. These treatments instead reduce the risk of breast cancer down the road. Since treatment of DCIS after surgery doesn’t improve survival, there is a growing concern that DCIS may be overtreated if the benefit of these treatments is outweighed by ... [[5]](https://www.cuimc.columbia.edu/news/stage-zero-breast-cancer-whats-optimal-treatment-dci...