Two new studies shed light on the complexity of preventing subsequent breast cancer events in patients with ductal carcinoma in situ (DCIS).

One study suggests that at least 2 years of endocrine therapy (ET) may be needed to provide a sustained benefit in patients with DCIS, and the other study suggests young DCIS patients often choose to forgo ET.1,2 

Both studies were presented at the AACR Special Conference Rethinking DCIS: An Opportunity for Prevention?

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Longer Duration of ET Tied to Benefit

In one presentation, Gillian L. Hirst, PhD, of the University of California, San Francisco, discussed registry data suggesting a longer duration of ET after breast-conserving surgery (BCS) may be key to reducing the risk of ipsilateral and contralateral second events in patients with DCIS.1

Dr Hirst and colleagues developed a registry of patients with DCIS treated during 1985-2017. The registry included 1916 patients for whom surgery type, radiotherapy (RT) status, and receipt and duration of ET were known. 

Patients underwent BCS alone (n=401), received RT after BCS (n=572), received ET after BCS (n=152), received ET plus RT after BCS (n=252), or underwent mastectomy (n=539).  

The median follow-up was 8.2 years. When compared with BCS alone, all other treatments were associated with a reduced risk of second events in a multivariate analysis.  

When the researchers stratified receipt of ET by duration, patients taking more than 2 years of ET had a significant reduction in the risk of second events (hazard ratio [HR], 0.12; P =.04), but patients taking ET for less than 2 years did not (HR, 1.3; P =.55). 

Compared with patients who underwent BCS alone, those who received ET for more than 2 years had a numeric reduction in contralateral and invasive breast cancers at 10 years, though this was not significant (HR, 0.48). 

Patients who took ET for more than 2 years after BCS had a similar risk reduction as patients who received RT after BCS or combined ET and RT after BCS. Patients who took ET for less than 2 years had a similar event rate as patients who underwent BCS alone, Dr Hirst said.

Younger DCIS Patients May Reject ET

In another presentation, Megan E. Tesch, MD, of the Dana-Farber Cancer Institute in Boston, discussed data suggesting that young patients with DCIS may forgo ET even if they are eligible and the treatment is recommended.

The data suggest that young DCIS survivors are concerned about the risk of subsequent breast cancer events, but some would prefer to try and lower their future breast cancer risk through surgery and potentially healthy behaviors rather than by taking tamoxifen.

To investigate treatment decisions, cancer preventive behaviors, and fear of recurrence among young DCIS survivors, Dr Tesch and colleagues surveyed participants in the Young Women’s Breast Cancer Study.

The cohort is a prospective registry of women aged 40 years and younger at diagnosis enrolled from 13 academic and community sites in the United States and Canada during 2006-2016.3 

The current analysis included 89 patients with DCIS who completed questionnaires at baseline and/or 6 months.2 In this cohort, 24.7% of patients underwent BCS, 18.0% had unilateral mastectomy, and 57.3% had bilateral mastectomy. 

Questionnaires at baseline showed that 65% of patients who underwent BCS, 50% of those who underwent unilateral mastectomy, and 29.4% of those who underwent bilateral mastectomy were “moderately to very concerned” about breast cancer recurrence.

BCS was offered to 46% of patients who had unilateral mastectomy and 76% of those who had bilateral mastectomy. Most patients who had bilateral mastectomy reported that the decision about surgery was mainly theirs (64%) and that they were highly confident in that decision (80% extremely confident and 18% very confident).