This year’s San Antonio Breast Cancer Symposium (SABCS) featured multiple thoughtful presentations centering around safe de-escalation of care from a local therapy management perspective, while using increasingly targeted adjuvant therapy for systemic cancer control. During Session 2, possible practice-changing preliminary data was shared on the treatment of low-risk ductal carcinoma in-situ (DCIS) of the breast by Dr. Shelley Hwang, MD, MPH.
In DCIS (or preinvasive breast cancer), the malignant cells are still contained within the milk-producing ducts of the breast without any evidence of invasion in the surrounding tissue. Over 56,000 cases of DCIS were diagnosed in the U.S. alone in 2024. The majority of these cases were diagnosed by pathological evaluation of a breast biopsy of “suspicious” microcalcifications seen on mammography, though, rarely, DCIS can be seen as a mass on imaging.
As Dr. Hwang, Mary and Deryl Hart Distinguished Professor of Surgery at Duke University School of Medicine, discussed during the first of two presentations dedicated to this issue, most patients diagnosed with DCIS are currently treated in a manner similar to invasive breast cancer, namely by surgical excision with or without radiation therapy and endocrine therapy in order to prevent future progression to invasive carcinoma. However, although DCIS is considered a precursor to invasive carcinoma, it is thought to be what is called a nonobligate precursor, meaning that only some cases, but not all of them, may progress to invasive cancer. This presents an opportunity for active monitoring (AM) for patients with DCIS with good prognosis instead of standard-of-care surgical excision.
Dr. Hwang shared two-year data from comparison of operation to monitoring with or without endocrine therapy (COMET), a prospective randomized noninferiority study comparing guideline-concordant care to active monitoring in patients with low-risk DCIS. COMET randomly assigned 995 patients with nuclear grade 1 or 2, HR+ DCIS with no evidence of invasive cancer to undergo active monitoring (n=484) or receive guideline-concordant care consisting of surgery with or without adjuvant radiation (n=473). Patients in the active monitoring arm could elect to have surgery at any time, and surgery was required if the tumor showed signs of invasive progression. The AM group was followed closely with mammograms every six months, with biopsies performed for any radiologic change. Endocrine therapy was allowed for patients in either arm.
Dr. Hwang reported that at two years, women with low-risk DCIS randomized to AM had a similar rate of invasive cancer in the ipsilateral breast compared to those randomized to standard care, raising the exciting possibility that carefully selected patients with DCIS may be able to safely omit surgery for DCIS. While she clarified that additional long-term data are needed to assess interval cancer development, these preliminary data help assuage fears that AM is an unsafe approach and offers possibility for future changes in the way we treat DCIS.
Accompanying Dr. Hwang’s thought-provoking presentation was a second presentation by Ann Partridge, MD, MPH, professor of medical oncology at Harvard Medical School, focused on patient-reported outcomes (PROs) from the COMET study. This presentation reported prospectively collected validated questionnaires, administered in person or virtually, at enrollment, six, 12, and 24 months to share the patient perspective on engaging in AM versus standard care of DCIS.
Dr. Partridge reported that at two years, overall quality of life, anxiety, depression, breast cancer worries, and symptom trajectories were comparable between patients who received the current standard-of-care treatment and those who underwent active monitoring with COMET. Similarly, long-term data are coming, but the equivalent patient-reported outcomes, including regarding anxiety and fear about treatment, are encouraging and suggest that patient choice should be prioritized in decision-making. Voicing the thoughts of many in the audience, she also thanked the SABCS for selecting the abstract for presentation as “a testament to their dedication to infuse the patient voice into the conference.”
Overall, the results of the DCIS COMET two-year analyses at SABCS 2024 by Dr. Hwang and Dr. Partridge provide exciting preliminary data regarding safe, less-invasive options for the treatment of patients with low/intermediate grade DCIS of the breast. Additional long-term data will confirm safety and patient satisfaction to allow for eventual incorporation of findings into clinical care.
Dr. Kalliopi Siziopikou is a professor of pathology and medicine and director of breast pathology at Northwestern University. Dr. Siziopikou has no financial interests or conflicts of interest to report.
Dr. Ellie Proussaloglou is an assistant professor of breast surgical oncology at Yale University. Dr. Proussaloglou has no financial interests or conflicts of interest to report.
Illustration by April Brust
