Active Monitoring Is Not Inferior to Surgery With or Without Radiation in Women With Low-Risk DCIS

In women with low-risk ductal carcinoma in situ (DCIS), is active monitoring for evidence of invasive progression noninferior to guideline-concordant usual care, including surgery with or without radiation?

At 2 years of follow-up, the study found that active monitoring in women with low-risk DCIS was not inferior to current guideline-based usual care (surgery with or without radiation). Results were similar in women who initiated endocrine therapy. The investigators will report further results to assess the continued safety and patient acceptability of active monitoring. (Level of Evidence = 1b−)

DCIS is conventionally treated with surgery, with or without radiation or endocrine therapy, similar to low- to intermediate-risk invasive cancer. The investigators identified women with newly diagnosed, screen-detected low-risk DCIS (hormone receptor–positive grade 1 or 2 without evidence of invasive cancer). Eligible patients (n = 957; median age 64 years) were randomly assigned to guideline-concordant usual care or active monitoring. Guideline-concordant usual care included surgery with or without radiation treatment depending on choice of surgery. Diagnostic mammography was performed every 12 months for the affected and unaffected breast. Active monitoring consisted of diagnostic mammography every 6 months for the affected breast and every 12 months for the unaffected breast. Patients with physical examination or imaging findings concerning for disease progression underwent core needle biopsy and surgery for identified invasive cancer.

Using intention-to-treat analysis, the 2-year cumulative rate of invasive cancer was similar in the guideline-concordant care and active monitoring groups (5.9% vs 4.2%, respectively), which supports the noninferiority of active monitoring. The tumor size of invasive cancers and the rate of all-cause mortality did not differ between groups. Results were similar in the subgroup of women who initiated endocrine therapy.

Study design: Randomized controlled trial (single-blinded)

Funding source: Government

Allocation: Uncertain

Setting: Outpatient (specialty)

Reference: Hwang ES, Hyslop T, Lynch T, et al.; COMET Study Investigators. Active monitoring with or without endocrine therapy for low-risk ductal carcinoma in situ: the COMET randomized clinical trial [published online December 12, 2024]. JAMA.