The COMET Study (Comparing an Operation to Monitoring, With or Without Endocrine Therapy for Low-Risk DCIS)
Key Points (2-year Results)
Question What is the short-term safety of an active monitoring approach vs guideline-concordant care (surgery with or without radiation therapy) for hormone receptor–positive, grade 1 or grade 2 breast ductal carcinoma in situ?
Findings In this prospective randomized clinical trial of 957 participants, the 2-year Kaplan-Meier cumulative rate of ipsilateral invasive cancer was 5.9% in the guideline-concordant care group vs 4.2% in the active monitoring group, a difference of −1.7% (upper limit of the 95% CI, 0.95%), indicating that active monitoring is not inferior to guideline-concordant care.
Meaning These data support the short-term safety of active monitoring compared with guideline-concordant care in patients with low-risk ductal carcinoma in situ.
COMET trial: active monitoring is a viable option for some patients with low-risk DCIS (Short video):
A new study published in the British Medical Journal (BMJ), July 2025, adds to growing evidence that many women with a DCIS diagnosis may want to consider an active monitoring approach.
The study followed nearly 1,800 women in the U.S. who chose not to have surgery right away after a DCIS diagnosis. Researchers wanted to see how many of these women developed invasive breast cancer and how many died from breast cancer over time. The women were followed for about 4–8 years.
Summary of Key Findings
- Low-risk DCIS: about 8 in 100 developed invasive cancer.
- Higher-risk DCIS: about 14 in 100 developed invasive cancer.
- Fewer than 2 in 100 women died from breast cancer over those 8 years.
- Overall, most women lived and did not develop invasive cancer, even without immediate surgery.
Cancer outcomes in women without upfront surgery for ductal carcinoma in situ: observational cohort study, BMJ, July 2025
PRECISION (PREvent ductal Carcinoma In Situ Invasive Overtreatment Now)
Low-Risk DCIS Research Update and Resources by PRECISION Patient Advocates
PRECISION launches a Series of Plain Language Summaries
PRECISION Impact Report
CGC-Impact-Report-Team-PRECISION-Final (1)
“Cancer Grand Challenges funding enabled us to transform understanding of DCIS biology and develop new approaches that could aid risk assessment to avoid overtreatment. We are empowering patients and clinicians to make more informed decisions about care.” – Jelle Wesseling PRECISION Team Lead, Senior Group Leader, The Netherlands Cancer Institute and Professor of Breast Pathology, Leiden University Medical Center.
Fellow COMET and PRECISION Patient Advocate Deborah Collyar is also a patient advocate for IMPROVE DCIS (Identify Molecular Predictors of Risk to Objectively Validate the Evolution of DCIS.)
Her blog Time for a DCIS Update provides patient friendly overviews and Plain Language Summaries (PLS) of the latest DCIS Research
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DCIS 411 is the only website and resource focused specifically on helping women understand the controversies with DCIS from a patient-centered perspective.
DCIS 411 FAQ provides links and resources to common questions — some of which are outside the “standard of care” box.