Neoadjuvant Endocrine Therapy Use in Estrogen Receptor Positive Breast Cancer: Insights from Practice Shifts During the COVID-19 Pandemic.

Publication date: Sep 20, 2025

The COVID-19 pandemic restricted operating room availability, prompting the Pandemic Breast Cancer Consortium to issue guidelines on deferring non-urgent surgical procedures. This led to an increased use of neoadjuvant endocrine therapy (NET) for estrogen-receptor positive (ER+) breast cancers. Irrespective of the pandemic, the ACOSOG Z1031 trial demonstrated that NET was effective at downstaging 51% of patients initially ineligible for breast conserving surgery (BCS). Despite this, NET utilization remains low. This study investigates NET use and related outcomes before, during, and after the pandemic. Patients aged ≥ 18 with clinical T1-T4c, N0-3, ER+/HER2- breast cancers were selected from the National Cancer Database and stratified into two groups: NET versus surgery first. The study analyzed trends from 2019 (pre-pandemic) to 2021 (tail-end-pandemic). Logistic regression identified factors associated with NET utilization. Results showed that 10,935 (3. 9%) patients received NET and 272,546 (96. 1%) underwent surgery first. NET use peaked in 2020 at 6. 4% (vs. 2019 2. 3% and 2021 3. 2%, P = 0. 001). Median time from diagnosis to treatment was significantly shorter in the NET group (1. 02 vs. 1. 35 months, P = 0. 001). Patients with clinical T3-4 disease who received NET versus surgery first had similar rates of BCS and were less likely to receive chemotherapy. The use of NET nearly tripled during the COVID-19 pandemic and was associated with decreased time to treatment and less use of adjuvant chemotherapy. NET could be considered for patients requiring a delay to surgery or for those with higher T-category who desire BCS or are unable to tolerate chemotherapy.

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