Among patients with hormone receptor–positive, HER2-negative, low-risk ductal carcinoma in situ (DCIS), those who underwent active monitoring had similar 2-year invasive ipsilateral breast cancer recurrence rates as those who underwent guideline-concordant treatment, according to results from the COMET trial presented at the 2024 San Antonio Breast Cancer Symposium (Abstract GS2-05).
E. Shelley Hwang, MD, MPH
A steady increase in mammography and other breast cancer screening methods has led to the identification of more cases of DCIS, which poses little risk to the patient unless it progresses to invasive disease, explained E. Shelley Hwang, MD, MPH, the Mary and Deryl Hart Distinguished Professor of Surgery, Vice-Chair of Research in the Department of Surgery, and Professor of Radiology at Duke University School of Medicine, who presented the study.
“All current treatments for DCIS aim to reduce the risk of future invasive cancer, despite a growing body of evidence that not all DCIS is destined to progress,” Hwang said. “Thus, current practice may result in the overtreatment of women whose tumors are at low risk of progression, leading to chronic pain, altered body image, reduced quality of life, and other side effects that may be avoidable.”
Study Details
The COMET investigators sought to assess whether active monitoring is as effective as upfront treatment among patients whose DCIS has a low risk of progressing to invasive cancer. They conducted a multicenter, randomized clinical trial that enrolled 995 patients with grade 1 or 2, hormone receptor–positive, HER2-negative DCIS with no evidence of invasive cancer. They randomly assigned 473 patients to undergo active monitoring and 484 patients to receive guideline-concordant care consisting of surgery with or without adjuvant radiation.
Patients in the active monitoring arm could elect to have surgery at any time, and surgery was recommended if the tumor showed signs of invasive progression. Patients in both treatment arms were allowed to receive endocrine therapy, if desired.
After 24 months of follow-up, 27 patients in the guideline-concordant care arm and 19 in the active monitoring arm had been diagnosed with invasive ipsilateral breast cancer. The 2-year cumulative rate of invasive ipsilateral breast cancer was 5.9% in the guideline-concordant care arm and 4.2% in the active monitoring arm; the difference met the threshold for noninferiority.
Because 46% of patients assigned to the guideline-concordant care arm declined surgery, the researchers performed a separate analysis of 673 patients who adhered to their assigned treatment. The 2-year rate of invasive ipsilateral breast cancer was 8.7% in the guideline-concordant care arm and 3.1% in the active monitoring arm, a difference that was not statistically significant.
Slightly more patients received endocrine therapy in the active monitoring arm compared to the guideline-concordant care arm—71.3% vs 65.5%, respectively. Among patients who received endocrine therapy, the rate of invasive ipsilateral cancer was 7.15% in the guideline-concordant care arm and 3.21% in the active monitoring arm.
Additional Perspective
Dr. Hwang noted that these results may help patients and their providers make informed decisions about how to proceed with DCIS treatment. “Omission of surgery has been highly controversial, with both patients and providers fearing that it might result in an unacceptably high rate of patients who develop invasive cancer,” Hwang said. “Our findings are reassuring, and longer-term follow-up will have important implications for the future inclusion of active monitoring as a treatment option for low-risk DCIS.”
Limitations of this study included the inability to blind treatment arms to either the provider or the patient. Further, although the researchers prospectively balanced patient characteristics between the two treatment arms, they noted that differences in characteristics that were unaccounted for are possible.
Disclosure: Funding for this study was provided by the Patient-Centered Outcomes Research Institute, the Breast Cancer Research Foundation, and Alliance Foundation Trials. Dr. Hwang reported no conflicts of interest.
