Estrogen Receptor-negative Ductal Carcinoma In Situ (DCIS) of the Breast – an Institutional Review of Outcomes

Background/Aim: Estrogen receptor (ER)-negative [ER(–)] invasive breast cancers (IBCs) are known to be more aggressive than their ER(+) counterparts. This is less well defined for ductal carcinoma in situ (DCIS). This study investigated the outcomes following the treatment of ER(–) DCIS. Patients and Methods: A total of 103 ER(–) DCIS patients diagnosed between 2004-2018 were retrospectively analyzed. Median follow-up was 63.9 months. Statistical analysis included descriptive statistics, non-parametric tests, T-test, logistic regression. The outcomes were compared to a group of 102 ER(+) DCIS patients from our institution. Results: Any breast event (BE) occurred in 10 (9.7%) patients at a median of 3.2 (1.7-7.2) years. The incidence of ipsilateral breast events (IBEs) was 5.8% (6/103). All IBE cases were ER(–) DCIS. All (n=4) contralateral breast events (CBEs) were ER(+) including 3 IBCs. Cumulative incidence of any BEs at 1, 2, and 5 years was 0%, 1.1%, and 9.1%, respectively. Among patients with ER(–) DCIS who developed BE, breast conserving surgery (BCS) had been performed for the initial DCIS in 90% of cases. In those without any BE, the BCS rate (vs. mastectomy) was 58.1% (p=0.08). Adjuvant radiotherapy after BCS was used less often among patients with vs. without subsequent BE (55.5% vs. 77.4%) (p=0.22). Predictors for BE occurrence were not identified. The incidence of any BE among patients with ER(+) DCIS was 6.9% and was not significantly different compared to ER(–) DCIS group (p=0.46). Conclusion: ER(–) DCIS outcomes were similar to our institutional ER-positive DCIS group and the previously reported ones for predominantly ER-positive DCIS cohorts.