Abstract OT1-10-01: The Breast Cancer Index registry study: A prospective multi-center observational study to evaluate patient outcome, clinical impact, and medication adherence in HR+ breast cancer patients considering treatment with extended endocrine therapy
Authors: O'Shaughnessy Joyce A , Fox Jenny R , Encarnación Carlos A , O'Neal Brandon , Treuner Kai , Sanft Tara , Jankowitz Rachel C , Pegram Mark D , Schnabel Catherine A , Diab Sami G 
Published: March 2022

Abstract
Background: Hormone receptor-positive (HR+) is the most common molecular subtype of breast cancer accounting for approximately 2 out of every 3 patients. Adjuvant anti-estrogen therapy is the cornerstone of systemic therapy, underscoring the critical role of endocrine treatment which affects the majority of women with breast cancer. Furthering efforts to better understand endocrine response and resistance and implementing genomic tools to help individualize patient selection for endocrine therapy are of ongoing importance to improve outcomes. Breast Cancer Index (BCI) is a gene expression signature composed of the Molecular Grade Index (MGI) and HOXB13/IL17BR (H/I) that predicts the likelihood of extended endocrine benefit and quantifies the risk of both late (5-10 years) and overall (0-10 years) distant recurrence. BCI has recently been incorporated into the NCCN clinical practice guideline as a biomarker for prediction of benefit from extended endocrine therapy in patients with early-stage, HR+ breast cancer. The objective of the BCI Registry Study is to collect real-world evidence at a national level aimed at advancing patient care and optimizing duration of endocrine treatment and will be conducted in two phases. First, long-term patient outcomes and the impact of BCI on decision-making based on physician and patient reported outcomes as well as medication adherence to extended endocrine therapy will be assessed. Secondly, individual patient data on over 40 clinical variables will be collected and partnered with molecular profiling and genomic data for each patient to enable correlative analysis and novel biomarker research of endocrine sensitivity and resistance. Study Description: The BCI Registry Study is a prospective, multi-center, observational data registry and biospecimen repository for stage I-III HR+ breast cancer patients. The main objective of the Registry Study is prospective characterization of BCI predictive and prognostic performance. The primary endpoint is time to distant recurrence (TTDR), defined as the interval between the time of BCI testing and the first metastasis at distant organs. Secondary endpoints include time to any recurrences and medication adherence score over time. Eligibility criteria includes confirmed diagnosis of HR+ early-stage invasive breast carcinoma (ductal, lobular, or mixed ductal/lobular), either HER2 negative or positive and either node-negative or node-positive tumors with 1-3 positive lymph nodes (N1). Patients must have completed 4 to 7 years of primary adjuvant endocrine therapy and have pre-treatment tumor tissue available from a previous breast surgery or biopsy. Both physicians and patients will complete a pre- and post-test Decision Impact Questionnaire to assess the impact of BCI results on extended endocrine therapy decision-making. Patients who elect to complete 10 years of endocrine therapy will answer a Medication Adherence Questionnaire during annual follow-up visits. Follow-up of patients will end 10 years from initial breast cancer diagnosis. The Registry plans to enroll approximately 3,000 patients across approximately 40 study sites in the United States. Enrollment for the study began in Q2 2021, and 324 patients have been enrolled as of July 2021. For more information, please visit the ClinicalTrials.gov registration: NCT04875351.
Citation Format: Joyce A O'Shaughnessy, Jenny R Fox, Carlos A Encarnación, Brandon O'Neal, Kai Treuner, Tara Sanft, Rachel C Jankowitz, Mark D Pegram, Catherine A Schnabel, Sami G Diab. The Breast Cancer Index registry study: A prospective multi-center observational study to evaluate patient outcome, clinical impact, and medication adherence in HR+ breast cancer patients considering treatment with extended endocrine therapy [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT1-10-01.