Abstract P1-02-03: Real World Treatment Patterns of Adjuvant Endocrine Therapy and Ovarian Suppression in Premenopausal HR+/HER2+ Breast Cancer
Authors: Sukumar Jasmine S. , Sardesai Sagar , Ni Andy , Williams Nicole , Ramaswamy Bhuvaneswari , Wesolowski Robert , Cherian Mathew A. , Stover Daniel , Gatti-Mays Margaret , Pariser Ashley C. , Sudheendra Preeti K. , George Mridula A. , lustberg maryam 
Published: March 2023

Background: Approximately 10% of breast cancers (BC) are hormone receptor positive (HR+) and HER2 positive (HER2+). Despite treatment advances in the modern era of HER2 targeted therapies for early-stage disease, there remains a risk for late relapses. However, the role of adjuvant endocrine therapy (ET) to reduce recurrence in this BC subtype is unclear. Oncologists employ clinical judgment given lack of consensus, resulting in differences in treatment patterns. The ideal endocrine agent including the role of adding ovarian suppression (OS) in premenopausal women is unknown. These patients are largely underrepresented in clinical trials such as the phase III SOFT and TEXT studies. Additionally, these trials were initiated prior to the widespread use of trastuzumab with chemotherapy, which is now standard of care for HER2+ disease. We aimed to describe real world patterns surrounding choice of adjuvant ET and clinicopathologic features which predicted treatment with OS in premenopausal women with HR+/HER2+ BC.

Methods: We performed a multi-institutional retrospective analysis of premenopausal women with non-metastatic HR+/HER2+ BC in the American Society of Clinical Oncology CancerlinQ® Discovery database from January 2010 to May 2020. Electronic health record data was obtained from 74 participating academic and community oncology sites. We collected clinical data on women less than 50 years who received chemotherapy, anti-HER2 therapy (trastuzumab with or without pertuzumab), and ET. Adjuvant OS was defined as receipt of at least 6 months of goserelin or leuprolide or surgical bilateral oophorectomy. Demographics, clinical characteristics, and treatment history was collected. Patients were categorized into 1 of 4 groups based on type of adjuvant ET prescribed at treatment initiation: aromatase inhibitor (AI) + OS, OS, tamoxifen + OS, or tamoxifen. Multivariable logistic regression was conducted to assess the association between clinicopathologic features and OS use.

Results: Out of 360,540 patients with invasive breast cancer in the database, 937 met inclusion criteria. Mean age was 41.7 (SD 5.9) years; 83% had stage 1 or 2 BC and 78% had node positive disease. The majority (n=818, 87%) were prescribed tamoxifen whereas only 4 (0.4%), 50 (5.3%), and 65 (6.9%) received OS, tamoxifen + OS, and AI + OS, respectively. Table 1 includes demographic and clinical characteristics of the cohort. No clinicopathologic features predicted OS use apart from age; patients ≥35 years were less likely to receive OS compared with those &lt; 35 (p&lt; 0.001) (table 2).

Conclusion: To our knowledge, this is the first real world study evaluating OS treatment in HR+/HER2+ BC. The use of OS was uncommon; this suggests a perception of its limited benefit when added to HER2-targeted therapy. Most patients received tamoxifen as the ET of choice. Age was the only factor to predict OS treatment; high risk features including node positivity and higher stage was not associated with its use. This highlights the wide variability in real world practice surrounding the clinical indications for OS. Further investigation is warranted to characterize the utility of ET including addition of OS to prevent recurrence in premenopausal HR+/HER2+ BC. This will better inform a personalized approach to tailor therapy for optimal outcomes in this distinct BC subtype.

Table 1. Demographic and clinical characteristics of study participants by endocrine therapy treatment group.

Table 2. Multivariable logistic regression model of clinicopathologic characteristics to predict use of ovarian suppression.

Citation Format: Jasmine S. Sukumar, Sagar Sardesai, Andy Ni, Nicole Williams, Bhuvaneswari Ramaswamy, Robert Wesolowski, Mathew A. Cherian, Daniel Stover, Margaret Gatti-Mays, Ashley C. Pariser, Preeti K. Sudheendra, Mridula A. George, maryam lustberg. Real World Treatment Patterns of Adjuvant Endocrine Therapy and Ovarian Suppression in Premenopausal HR+/HER2+ Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-02-03.