De-Escalation of Endocrine Therapy After Mastectomy for Ductal Carcinoma In Situ

Ductal carcinoma in situ (DCIS) of the breast may be treated locally with either breast conservation therapy, involving segmental mastectomy followed by radiation, or total mastectomy. Per current guidelines, hormone-positive DCIS is then treated systemically with adjuvant endocrine therapy (aET). We sought to determine whether a significant benefit exists for aET following both bilateral and unilateral total mastectomy for DCIS.

We conducted a retrospective cohort study of DCIS cases treated surgically with mastectomy between 2010 and 2022 at a high-volume academic cancer center. Only patients diagnosed with pure DCIS on final surgical pathology were included in this analysis. We evaluated recurrence rates and survival outcomes after unilateral total mastectomy (UTM) or bilateral total mastectomy (BTM) performed for DCIS, with or without aET.

A cohort of 290 patients were included and evaluated, 46 underwent BTM and 244 underwent UTM. In BTM group, mean age (± standard deviation) was 55.8 ±12 years and median follow-up duration & interquartile range (IQR) was 58 (27-96) months. For BTM, 40 patients (87%) did not receive aET, with no reported recurrences and one mortality unrelated to breast cancer. In UTM group, mean age was 61.1+12 years, and median follow-up time was 61 (IQR 37.5-94) months. For UTM, 158 patients (65%) did not receive aET, with two recurrences (1%), one mortality due to metastatic breast cancer and 13 mortalities unrelated to breast cancer. For UTM, 82 patients (35%) received aET, with one recurrence (1%), with subsequent breast cancer related mortality and five mortalities unrelated to breast cancer.

Our data demonstrated no significant oncologic benefit related to aET for patients with pure DCIS on final surgical pathology, following either BTM or UTM, at 5-year follow-up. This conclusion supports the current recommendation for individualized discussion of the risks related to side effects versus benefits including risk reduction in the contralateral breast in the setting of UTM and reduction of invasive systemic recurrence in this specific cohort. Further investigation examining the balance of potential side effects and impact on compliance of aET is needed to understand this risk benefit ratio and to improve treatment guidelines.