Abstract PO4-01-14: Effects of neoadjuvant endocrine therapy on early-stage breast cancer: a retrospective cohort study of patients during the COVID19 pandemic

Abstract Background: At the height of the COVID19 pandemic, many surgical procedures across the country including at Dartmouth-Hitchcock Medical Center (DHMC) were postponed to redirect resources. The American Society of Breast Surgeons shared guidelines to manage patients experiencing surgical delays. For estrogen receptor positive (ER+), HER2- early-stage tumors, recommendations were to use neoadjuvant endocrine therapy (NET). NET is usually under-utilized for locally advanced hormone receptor-positive breast cancer (BC) despite literature concluding that chemotherapy and NET have comparable clinical response rates but with lower toxicity for the latter. The COVID19 pandemic thus presented a unique occasion to extend the use of NET for localized BC. Herein, we examined the rate of adoption of NET and associated patient/tumor characteristics at DHMC during the lockdown. Methods: A retrospective analysis of patients diagnosed with early-stage ER+, HER2- BC between December 2019 and June 2020. Data extracted from chart review included age, menopausal status, tumor stage/grade, body mass index (BMI), and adherence to adjuvant endocrine therapy (ET). A “delay in surgery” was defined as days between surgical consult and surgery over 14 days. Descriptive statistics were applied to data collected on patient/tumor characteristics, and the number of patients accepting or declining NET. Results: 109 cases were identified within the study period, with 42 found with surgical delay. The median age of the delayed group was 62 and the majority of patients were post-menopausal. 36 patients received NET with most started on an aromatase inhibitor. Median BMI was 28.5. Median duration of treatment was 39.5 days. Three cases were noted to have some decrease in cellularity for pathologic partial response and four had no definite response. The majority of patients on NET had no change in pathological grade. Out of the 36 patients who had NET, 30 (83.3%) remain on adjuvant ET. In contrast, only 59% (43 out of 73 patients) of those who did not receive NET were on adjuvant ET at the median follow up time of 2.75 years post-therapy initiation. Of note, 16 (out of 73) patients who were not on NET were either lost to follow up, had their care transferred to another health network or were not offered ET. Results are reported in Tables 1 and 2. Conclusions: Delays in surgery during the COVID19 crisis resulted in increased use of NET in early-stage BC. Impact of NET use includes possible increase in long-term adherence to adjuvant ET with a trend towards statistical significance (odds ratio of 3.25, p=0.08). A larger sample size is needed to evaluate this finding and a prospective trial is in progress (NCT04568616). NET is a viable treatment option during surgical delays and may help increase long-term adherence to adjuvant ET. Table. Patient and tumor characteristics Table. Number of patients on adjuvant ET Citation Format: Mary Chamberlin, Todd Miller, Marie Anne Christine Buteau, Steven Tau. Effects of neoadjuvant endocrine therapy on early-stage breast cancer: a retrospective cohort study of patients during the COVID19 pandemic abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-01-14.