COMET stands for Comparing an Operation to Monitoring, with or without Endocrine Therapy for low-risk DCIS. This is the first large phase III randomized clinical trial in the United States (US) to look at different management strategies for low-risk DCIS. The COMET Study will enroll 1200 women with low-risk DCIS at about 100 sites throughout the US. The study is funded by the Patient-Centered Outcomes Research Institute (PCORI).