Abstract P1-08-33: Disparities in the practice of precision medicine? Using multi-gene testing in early-stage, HR+/HER2- breast cancer
Authors: Bilani Nadeem , Yaghi Marita , Saravia Diana , Jabbal Iktej , Zerdan Maroun Bou , Elson Leah , Hong Liang , Nahleh Zeina 
Published: March 2022

Background: Multi-gene testing (MGT) can be used to identify patients with early-stage, hormone receptor-positive (HR+), HER2-negative (HER2-) breast cancer that are likely to benefit from treatment regimens with chemotherapy and endocrine therapy, compared to endocrine therapy alone. Two examples of genomic panels include OncotypeDX (ODX) MammaPrint (MP). Tailoring practice to the unique profile of each patient, known as ‘precision medicine’, has significantly refined the treatment approach in breast cancer, while decreasing toxicity and cost. In this analysis, we explore disparities in the access to precision medicine among several socio-demographic groups. Methods: We conducted a retrospective analysis of the National Cancer Database, using the 2004-2017 breast cancer dataset. We included patients with HR+/HER2-, stage I-II breast cancer. We excluded patients with stage III disease as many would still receive chemotherapy with less use of MGT. Using chi-squared statistics, we identified socio-demographic, clinical and pathologic factors associated with the use MGT - either ODX or MP - in this group. We then included significant variables (p&lt;0.05) in one multiple logistic regression model predicting the use of either genomic panel. Results: A total of n=841,716 patients who were candidates for MGT (early-stage, HR+/HER2- breast cancer) were included in this analysis. N=283,833 (n=33.7%) underwent MGT (32.2% used ODX while 1.5% used MP). Use of genomic assays has increased significantly over time (11.5% for patients diagnosed between 2007-2009, to 39.4% between 2016-2017). Variables significantly associated with the use of either ODX/MP at the multivariate level (p&lt;0.05) included: age, race, insurance status, education level, facility type, year of diagnosis, geographic location, tumor grade, and tumor histology. Elderly patients (&gt;70) were less likely than those &lt;50 to undergo MGT (OR 0.32, 95% CI 0.32-0.33, p&lt;0.001). Black patients were also less likely to receive a genomic assay compared to White patients (OR 0.80, 95% CI 0.78-0.82, p&lt;0.001). Insurance status was another significant predictor, with uninsured patients being the least likely to receive ODX or MP (OR 0.69, 95% CI 0.66-0.72, p&lt;0.001), compared to those with private insurance. Conversely, patients treated at academic/research cancer programs were more likely to undergo MGT than those treated at community cancer programs (OR 1.13, 95% CI 1.10-1.15, p&lt;0.001). Geographic discordance in use of MGT was also identified: with highest rates of use (39.2%) in the Middle Atlantic (NJ, NY, PA), and lowest rates (23.5%) in West South-Central states (AR, LA, OK, TX). Conclusions: This large analysis of real world, national data identified several social determinants of health predictive of disparity in the implementation of precision medicine practices for early-stage, HR+/HER2- breast cancer. Improving access to innovative, diagnostic and prognostic tools, among black and underinsured patients, as well as those treated in community practices, is needed.

Citation Format: Nadeem Bilani, Marita Yaghi, Diana Saravia, Iktej Jabbal, Maroun Bou Zerdan, Leah Elson, Liang Hong, Zeina Nahleh. Disparities in the practice of precision medicine? Using multi-gene testing in early-stage, HR+/HER2- breast cancer [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 P1-08-33.