Active monitoring: A safe option for DCIS? | SABCS 2024

While these early results support the safety of this approach, they are unlikely to change practice right away. The full results were released on the same date in the Journal of the American Medical Association.

Background

Ductal carcinoma in situ (DCIS) is noninvasive, stage 0 breast cancer—cancer that has not broken through breast ducts into breast tissue. About 50,000 people in the United States are diagnosed with DCIS each year. DCIS does not always progress to invasive breast cancer.

Doctors do not entirely know if or when DCIS will become invasive. They can assign DCIS a grade of one to three to the DCIS based on how different the cancer cells look from normal cells:

• Grade one DCIS is considered low-grade, slow growing, and less likely to develop into invasive cancer.
• Grade two DCIS grows more quickly. It is likely to return after surgical removal. Grade two is also called intermediate.
• Grade three DCIS is the fastest growing of the three grades, with the highest likelihood of becoming invasive.

Overtreatment is a much-discussed topic in the breast cancer community. People who have been diagnosed with breast cancer, advocates, and healthcare professionals have raised concerns about the negative impact of treating certain cases of DCIS. This can include emotional distress, surgery risks, treatment-related side effects, and financial burden.

Active monitoring has long been used in other cancers, including blood cancers that can go years without growth. More recently, a “watch and wait “approach has become practice in prostate cancer. This is based on research showing that the potential for negative mental and physical effects of treatment may outweigh the benefits.

Results

This study, known as the COMET trial, primarily assessed safety. Is active monitoring a safe option for people with low-risk DCIS? These early results strongly suggest the answer is yes, but more follow-up is needed.

COMET is a randomized study comparing active monitoring with standard treatment in women diagnosed with hormone receptor-positive, grade one or two DCIS.

In this study, participants were relatively healthy women ages 40 and older. Three out of four were white while nearly 16% were Black and 9.3% were of an unknown or other race.

The study team was careful about selecting participants to avoid failing to treat people whose cancers were higher risk.

DCIS cells spanning four or more centimeters were biopsied in two sites. DCIS grade was confirmed by two pathologists.

Participants were randomly assigned to one of two groups—active monitoring (AM) or guideline concordant care (GCC). GCC included surgery and, in some cases, radiation therapy. People in both groups could choose to take hormonal therapy to reduce the risk of recurrence. All participants were tracked to see if they developed invasive cancer.

The results were similar and favored active monitoring. At two years, 5.9% of participants in the treatment group had developed invasive cancer versus 4.2% in the active monitoring group. The study team did not find any notable differences among the cancers.

The authors also looked at patient-reported outcomes. Participants answered questions at the start of the study, at six months, at one year, and annually thereafter. The questions addressed symptoms, anxiety, depression, pain, and quality of life. The findings were similar for both groups.

Nearly one-third of participants in this study did not stay in their assigned study arm and could not be considered in the results. In most cases, people originally assigned to the treatment group moved to the active monitoring group. This shift may reflect some bias in participation—people who were interested in active monitoring were more likely to join the clinical trial.

What does this mean for you?

This study addresses a concern raised by breast cancer advocates about potential overtreatment of breast cancer. The results are very promising but unlikely to change practice at this time, given that the study team only has two years of data. More follow-up is needed. Look for updates at five and seven years.

If you were recently diagnosed with DCIS and you have concerns about starting treatment, you may want to discuss this study with your doctors to explore your options. At minimum, the conversation could lead to stronger mutual understanding of treatment goals and expectations, and more effective shared decision-making.