Abstract PS2-04-01: Early Adoption of Molecular Residual Disease Testing in Breast Cancer Patients using Real World Data

Abstract Early Adoption of Molecular Residual Disease Testing in Breast Cancer Patients using Real World Data Authors: Ning Yan Gu1, Kohli M2, Stephen J Noga1, Quang A. Le1, Rodriguez-Silva J2, Barhoush Y2, Batchu L2, Gebra Cuyun Carter11Exact Sciences, Madison, WI, USA; 2STATinMED LLC. , Dallas, TXWord count: 2765/3400 characters OBJECTIVE: Testing for molecular residual disease (MRD) via circulating tumor DNA (ctDNA) biomarker is an emerging practice in cancer treatment and disease recurrence detection. This study aims to assess the early adoption of MRD for patients diagnosed with breast cancer (BC) using real-world data. METHODS: A national multi-payer medical and pharmacy claims data (STATinMED RWD Insights) with nearly 80% of the US healthcare system was used. Data were extracted for female patients aged ≥18 years between January 1, 2015, and November 30, 2023. Index date was defined as the first date of BC diagnosis. Included patients were required to have continuous enrollment for a minimum of 12 months pre-index, 30 days post-index, and had ≥1 inpatient or ≥2 outpatient BC claims (ICD-9-CM: 174x, 175x; ICD-10-CM: C50x). Patients were excluded if they had metastasized disease, other cancers (not including non-melanoma skin cancers), any BC treatment, or had evidence of pregnancy during the 12-month baseline period. Proxies were used to determine BC subtype and cancer stage. MRD utilization was identified from the index date to study end time and/or patients’ death. Multivariate logistic regression was used to identify predictors of the MRD test adoption. RESULTS: Among 652, 463 eligible patients (mean age: 65. 4 years), 815 (0. 12%) had evidence of MRD testing, the first one was in 2021, increased in 2022, and continued to the study end date of November 30th, 2023, with most of the MRD testing occurred in 2023 (n=748, 91. 8%). The mean follow-up time per patient was 38. 76 months (SD: 26. 57) with a median follow-up per patient of 29. 70 months. The mean age of MRD tested patients was 62. 7 years; 67. 7% were White; 60. 1% were non-Hispanic; 36. 0% had a college education; 51. 4% had Medicare; 27. 3% had an income below 25, 000 and 55. 5% resided in the Southern United States. Categorizing the subtype, 65. 2% had HR+/HER2- BC, 23. 3% had triple-negative BC (TNBC), and 9. 5% had HR+/HER2+ BC. During the study time frame, 60. 9% of patients received only one MRD test, 23. 1% received two, 8. 3% received three and the remaining 7. 7% of patients received four or more MRD tests, for up to 10 MRD tests. The mean number of MRD tests per patient was 1. 72 (SD: 1. 27). Among the 815 MRD-tested patients, 392 (48%) had evidence of breast-conserving surgery (BCS). Of those 392 patients, 5 (1. 3%) received MRD testing before the BCS and 387 (98. 7%) received MRD test after the BCS. For every BC subtype, the average time between tests was 80 days between the 1st and 2nd tests, 70 days between the 2nd and 3rd tests, with shorter intervening times for additional MRD tests conducted during study period. Based on the multivariate logistic regression, key factors associated with the receipt or adoption of MRD test included younger age, advanced BC stage, BC subtype, and patients’ residence region. CONCLUSION: This descriptive analysis using real-world data offers insights into the early adoption of the MRD testing among BC patients in the United States. The real-world evidence showcased an upward adoption trajectory during the study period and there were variations in early utilization patterns. Findings herein provide hypothesis generating opportunities for future investigations. Key Words: 1. Molecular residual disease 2. MRD testing 3. ctDNA 4. Breast cancer 5. Real world data Citation Format: N. Gu, M. Kohli, S. J. Noga, Q. A. Le, J. Rodriguez-Silva, Y. Barhoush, L. Batchu, G. C. Carter. Early Adoption of Molecular Residual Disease Testing in Breast Cancer Patients using Real World Data abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32 (4 Suppl): Abstract nr PS2-04-01.