The first results of the U.S-based Comparing an Operation to Monitoring, with or without Endocrine Therapy (COMET) trial, a phase III randomized clinical trial comparing different management strategies for low-risk DCIS, were released earlier this month. The findings were published in JAMA and JAMA Oncology and were presented at the 2024 San Antonio Breast Cancer Symposium.
The key takeaway from the study is that women with low-risk DCIS who underwent active monitoring instead of surgery were no more likely to develop invasive breast cancer in the affected breast after two years. The findings represent a first step toward a safe treatment de-escalation option for low-risk DCIS patients who might want to avoid surgery and radiation unless and until it becomes necessary.
About the Study
COMET followed 957 women over two years. To be eligible, study participants had to be aged 40 years or older with a new DCIS diagnosis of low or intermediate grade, hormone-receptor positive, HER2-negative, and no signs of invasive cancer. The DCIS must have been detected by a screening mammogram, and at least two pathologists had to agree on the diagnosis.
Participants were randomly assigned to one of two treatments arms:
- Guideline-Concordant Care (Surgery): At time of diagnosis, these women underwent the standard of care treatment of surgery (mastectomy or lumpectomy, with or without radiation).
- Active Monitoring: These women underwent mammograms and check-ups with their doctor every six months, and only had surgery if the DCIS progressed to invasive breast cancer (these women could also elect to have surgery at any time).
473 women were randomized to surgery and 484 women were randomized to active monitoring. Study participants were able to switch from their assigned treatment option if they so desired (these changes were anticipated by the researchers and statistically accounted for). All of the participants were given the option to take hormone therapy, and over 70% of the active monitoring arm and 65% of the surgery arm elected to do so.
Over the course of the trial, a secondary analysis was conducted analyzing how active monitoring impacted quality of life for DCIS patients. All trial participants were asked to complete patient-reported outcome questionnaires, which included questions about overall health and mental health-related quality of life, anxiety, depression, worry about DCIS, and symptoms related to treatment side effects.
Study Results
After two years of follow-up, the rate of invasive cancer for the women in the surgery arm was 5.9% (about 6 in 100 women) and the rate of invasive cancer in the active monitoring arm was 4.2% (about 4 in 100 women). The statistical difference met the standard for noninferiority, meaning that neither treatment arm was deemed inferior to the other.
In the patient-reported outcomes analysis, at the two year follow-up there was no significant difference between the two treatment arms in terms of overall health-related quality of life, anxiety or worry about DCIS. This data controverts previously-held assumptions that forgoing surgery would cause patients undue stress, and supports the notion that women should feel empowered to choose the treatment option that works best for them.
Why this Matters for DCIS Patients
The COMET results provide evidence that some low-risk patients may be able to safely manage their DCIS with active monitoring, at least in the short-term. Notably, the study results were limited to two years, and more follow-up is needed to confirm that active monitoring is safe over a longer time horizon. COMET trial participants will continue to be followed for several more years and the next results will be reported at the five-year mark. If the results hold up over time, it could transform the way we treat low-risk DCIS to include active monitoring as a safe alternative to the more aggressive treatments of surgery and radiation.
While active monitoring will not be medically-indicated or the personal preference for many women, COMET represents an exciting first step toward a future with more treatment choices for tens of thousands of low-risk patients. More broadly, it has the potential to reduce the overtreatment of DCIS and provide DCIS patients with more individualized, patient-centered care than they deserve.
Last Updated December 28, 2024
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