MONDAY, March 30, 2026 (HealthDay News) -- Active surveillance seems safe for women with estrogen receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative, grade 1 to 2 ductal carcinoma in situ (DCIS), according to a study presented at the annual European Breast Cancer Conference, held from March 25 to 27 in Barcelona, Spain.
Jelle Wesseling, M.D., from The Netherlands Cancer Institute in Amsterdam, and colleagues examined the safety of active surveillance versus standard treatment in women with estrogen receptor-positive, HER2-negative, grade 1 to 2 DCIS. The primary end point was the ipsilateral invasive breast cancer (iiBC)-free rate at 10 years. A total of 1,423 women were enrolled and followed for a median of 23 months. The first 73 patients were randomly assigned to active surveillance and standard treatment; the trial was transformed to a patient preference design, and 1,025 and 330 patients opted for active surveillance and standard treatment, respectively.
The researchers found that iiBC occurred in 1 and 6 percent of women allocated to standard treatment and active surveillance, respectively, on an intention-to-treat basis. The Data Safety Monitoring Board advised cessation of registration and recruitment based on these findings, with continuing follow-up of enrolled patients. When iiBCs detected at primary surgery in the standard-treatment group were considered, the cumulative incidence of iiBC was similar between strategies: 9 and 6 percent in the standard-treatment and active surveillance arms, respectively.
"For women with low-risk DCIS, these interim results are reassuring. There is currently no indication that active surveillance leads to worse early outcomes compared with immediate surgery," Wesseling said in a statement. "This study contributes important evidence to the discussion about reducing overtreatment in breast cancer care."