Abstract PS7-23: Neoadjuvant and adjuvant therapy (NAT/AT) treatment patterns and clinical characteristics in a real-world cohort of US patients with HR+/HER2− early breast cancer (eBC)
Authors: Downer Mary K , Craggs Christopher , Dhillon Preet , Luhn Patricia , Flores-Avile Carlos , Tan Amie , Patre Monika , Schimmoller Frauke , Crnjevic Tanja Badovinac 
Published: February 2021

Abstract
Background: Treatment patterns in hormone receptor (HR)+/human epidermal growth factor receptor 2 (HER2)− eBC continue to evolve. While AT remains the standard of care, NAT has been indicated as a viable approach to downstage higher-stage tumors. As interest in NAT trials increases, detailed data on current treatment patterns may inform future research. The objective of this retrospective observational study was to evaluate patient characteristics and treatment patterns in US patients diagnosed with HR+/HER2− eBC.
Methods: This analysis included adults diagnosed with non-metastatic (stage I-III) invasive eBC between January 1, 2011, and March 1, 2019, in the nationwide Flatiron Health electronic health record–derived de-identified database. All patients had HR+/HER2− test results within 90 days of eBC diagnosis and evidence of both primary surgery and systemic treatment in the eBC setting. Patients with records of HER2-targeted treatment were excluded. NAT was defined as systemic treatment before first primary surgery; AT was defined as systemic treatment within 12 months after primary surgery among patients with ≥ 6 months of follow-up after surgery. Pathologic complete response (pCR) was defined as the absence of residual invasive disease in the breast and axillary lymph nodes after NAT and was subsequently confirmed at the time of primary surgery.
Results: Among 4739 patients in the study, 341 (7%) received NAT (318/341 received AT following NAT) and 4398 (93%) received AT only. The proportion of patients receiving NAT increased annually from 5% in 2011 to 9% in 2018. Of NAT-treated patients, 7% achieved pCR. Patients who had higher pathology stage, higher tumor grade, younger age and who were Black or Hispanic/Latino had higher proportions of NAT (Table). Patients who received NAT were more likely to receive a mastectomy (vs lumpectomy) compared with patients who received AT only. The most common NAT regimens included chemotherapy (54%; primarily anthracycline + cyclophosphamide + taxane [ACT] regimens) or endocrine (ET) monotherapy (36%; primarily aromatase inhibitor [AI]). The most common AT regimens were ET monotherapy (79%; primarily AI or tamoxifen).
Conclusions: Although AT remains the standard treatment approach in US clinical practice for HR+/HER2− eBC, interest in NAT has grown in recent years and NAT use has increased. Given the low pCR rates following NAT and since pCR is considered a surrogate marker for survival, further investigation into longer-term clinical benefits of NAT in this population is warranted as NAT may be becoming more common.
Table. Characteristics of patients with HR+/HER2− eBC who received AT or NATAT only(first treatment after surgery)N = 4398NAT(first treatment before surgery)N = 341pCR achievedYesNA25 (7.3)NoNA271 (79)UnknownNA45 (13)Age at eBC diagnosisMedian (IQR), years64 (54-72)59 (49-68)RaceNon-Hispanic White2975 (68)208 (61)Non-Hispanic Black278 (6.3)31 (9.1)Non-Hispanic Asian120 (2.7)13 (3.8)Non-Hispanic other428 (9.7)27 (7.9)Hispanic/Latino282 (6.4)39 (11)Unknown315 (7.2)23 (6.7)Year of eBC diagnosis2011/20121023 (23)53 (16)2013/20141136 (26)81 (24)2015/20161129 (26)101 (30)2017/2018/201911100 (25)106 (31)Pathology group stageI2370 (54)70 (21)II1209 (27)86 (25)III282 (6.4)58 (17)Unknown537 (12)127 (37)Tumor grade11268 (29)41 (12)22297 (52)186 (55)3768 (17)111 (33)Unknown65 (1.5)3 (0.9)HistologyIDC3486 (79)267 (78)ILC615 (14)51 (15)Other/Unknown297 (6.8)23 (6.7)Primary surgery typeLumpectomy2911 (66)128 (38)Mastectomy1487 (34)213 (62)Data are n (%) unless otherwise specified.AT, adjuvant chemotherapy; eBC, early breast cancer; IDC, invasive ductal carcinoma; ILC, invasive lobular carcinoma; NA, not applicable, NAT, neoadjuvant chemotherapy; pCR, pathologic complete response.* The number of patients diagnosed in 2019 is very low because we only included patients diagnosed through March 2019; thus 2019 is grouped with 2017/18.
Citation Format: Mary K Downer, Christopher Craggs, Preet Dhillon, Patricia Luhn, Carlos Flores-Avile, Amie Tan, Monika Patre, Frauke Schimmoller, Tanja Badovinac Crnjevic. Neoadjuvant and adjuvant therapy (NAT/AT) treatment patterns and clinical characteristics in a real-world cohort of US patients with HR+/HER2− early breast cancer (eBC) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-23.