Active Monitoring May Be as Good as Surgery for Low-Risk DCIS

Women with low-risk DCIS (ductal carcinoma in situ; also known as Stage 0 breast cancer) who receive active monitoring instead of surgery at the time of diagnosis appear no more likely to develop invasive breast cancer in the affected breast after two years. The findings of the COMET trial were presented at the 2024 San Antonio Breast Cancer Symposium and published in JAMA and JAMA Oncology.

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  The study included women aged 40 years and older who had been recently diagnosed with low-risk DCIS (defined as grade 1 or 2, hormone receptor-positive, HER2-negative).

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  After two years of follow-up, 5.9% of the women who received standard-of-care treatment (surgery with or without radiation) and 4.2% who were actively monitored (mammograms every six months) had been diagnosed with invasive breast cancer in the affected breast.

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  Women in either group could take hormonal therapy, which could have affected rates of invasive breast cancer in the affected breast.

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  The study is an important early investigation into DCIS treatment de-escalation — the practice of personalizing treatment for the best outcomes with the fewest side effects — but does not change the standard of care.

The results of the two-year analysis are encouraging: they suggest that some people with DCIS may be able to safely skip surgery and be managed with active monitoring. Still, it’s important to remember that invasive breast cancer can develop decades after a hormone receptor-positive DCIS diagnosis, and this study only focused on outcomes at two years. It remains to be seen if there will be differences in outcomes between the groups over longer periods of time.

The study’s lead author, E. Shelley Hwang, MD, MPH, of Duke University School of Medicine, acknowledged this during a press briefing at SABCS. “While these results are provocative, I don’t think they’re quite practice-changing yet,” she said. “I think the way [these findings] will change how we interact with patients … is that we can tell patients that their risk of invasive cancer is low, even with active monitoring. For those patients who’ve already decided … that they refuse to have surgery, I think we’ve come up with an active monitoring protocol that’s safe and clearly detects invasive cancers at a very early stage.”

More than 50,000 women are diagnosed with DCIS in the U.S. each year. Despite evidence that some DCIS doesn’t develop into invasive cancer, many people with the diagnosis choose to have surgery followed by radiation, hormonal therapy, or both. While all these treatments reduce the risk of invasive cancer in the affected breast, they do cause side effects, including chronic pain, sexual dysfunction, and more.

“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 in a press release. 

Hwang and colleagues wanted to know if there was a difference in the risk of invasive cancer among people with low-risk DCIS who received active monitoring and those who received surgery.

A total of 957 women (75% white and nearly 16% Black) with low-risk DCIS were divided into two groups: 

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  473 women received standard-of-care treatment, which included either lumpectomy or mastectomy, and radiation after surgery if recommended by their doctor. 

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  484 women received active monitoring, which consisted of a mammogram of the affected breast every six months and a biopsy if changes were seen.

Women assigned to the active monitoring group could elect to have surgery at any time. If invasive breast cancer was detected in women in the active monitoring group over the course of the study, they were required to have surgery and the invasive breast cancer diagnosis was recorded. 

All participants in the study were asked to complete patient-reported outcome questionnaires (these included questions about general health, anxiety and depression, and symptoms related to breast cancer treatment) over the course of the trial. 

After two years, 27 women in the standard-of-care group and 19 in the active monitoring group had been diagnosed with invasive cancer in the affected breast. 

Nearly 30% of the women in the study didn’t follow the treatment plan they were assigned to. When the researchers limited their analysis to only those who received their assigned treatment, they found that the two-year rate of invasive cancer was 8.7% in the standard-of-care care group and 3.1% in the active monitoring group.

A total of 65% women in the standard-of-care group and 71% women in the active monitoring group took hormonal therapy. It’s unknown what effect this had on the results.

Women in the group that received active monitoring and those in the surgery group reported similar overall quality of life, anxiety, depression, and symptoms during the two year follow-up.