De-Escalation of Surgery in Ductal Carcinoma In Situ

Clinicians have long known that not all ductal carcinoma in situ (DCIS) progresses to invasive cancer. Many women likely live out their lives harboring an underlying DCIS that never impacts their health. These observations have supported efforts to identify patients with low-risk subtypes of DCIS that could be candidates for de-escalation of standard interventions, including radiation therapy, adjuvant endocrine therapy, and now, surgery.

The noninferiority COMET trial compared outcomes between patients randomized to current guideline-concordant care (surgery with or without radiation therapy) or active monitoring without surgical intervention (breast imaging and physical exam every 6 months). Eligible participants were women aged 40 years and older with newly diagnosed, screen-detected, nuclear grade 1 or 2 ER/PR-positive, HER2-negative DCIS.

Of 997 women enrolled, 75% were white and 16% Black. At diagnosis, 75% had grade II DCIS and 25% grade 1. With a median follow-up of 37 months, 264 women in the guideline-concordant group and 82 in the active monitoring group underwent surgery. Ipsilateral invasive cancer was diagnosed in 27 women in the guideline-concordant group and 19 in the active-monitoring group. The 2-year cumulative rate of ipsilateral invasive cancer – the primary outcome — was 5.9% versus 4.2%, respectively; this result met the noninferiority threshold, thereby demonstrating short-term safety of active monitoring.