Background: Breast cancer is the most common cancer diagnosis in women. Metastatic breast cancer is difficult to treat and is a major cause of mortality related to breast cancer. Treatment includes therapeutic options that target specific molecular signals and pathways responsible for cancer growth and other malignant features. These advances have necessitated new biomarkers that can identify tumor molecular features to select the right patients who will maximally benefit from these therapies. Focused next-generation sequencing (NGS) on DNA isolated from the tumor tissue or circulating tumor DNA in the blood has quickly become standard of care to create actionable and personalized treatment plans. However, these tests are often expensive, limiting their clinical implementation. We hypothesized that limited access to these therapies increases health disparities in clinical oncology.

Objective: The aim of this study is to examine if neighborhood socioeconomic status (SES), as defined by area of deprivation index (ADI), as well as factors including race, ethnicity, and insurance status influence access to NGS testing in the Dallas area.

Methods: Data from 187 patients with recurrent MBC were obtained from the Dallas Metastatic Breast Cancer Study (DMBCS), a clinical database that was established in 2021 at a single academic medical system to track patient demographics, area deprivation index (ADI), race, ethnicity, treatments, and other variables that are not widely available in other national databases for MBC. Ethnicity was categorized into Hispanic versus non-Hispanic consistent with Office of Management and Budget census standards, and race was separated into White, African American, Asian American and Native Hawaiian/Pacific Islander. Commercial NGS testing was performed on patient tumor tissue or circulating tumor DNA from blood samples by Tempus and FoundationOne between the years 2014 through 2022.

Results and Discussion: Overall, 39% of patients in our dataset received NGS testing. Patients who are not Hispanic or Latino (n=140, OR: 3.99, 95% CI: 1.66-9.61) are about 4 times more likely to receive NGS compared to those who are Hispanic or Latino (n=42). Insurance, whether private (OR: 7.35, 95% CI: 2.29-33.08) or public (OR: 4.90, 95% CI: 1.55-21.81), also significantly increased the likelihood of receiving NGS testing compared to those without insurance. Interestingly, race was not a significant factor amongst White (n =131), African American (n=33), and Asian (n=8). Next, we sought to evaluate whether ADI would correlate with access to NGS testing. ADI measurements include education level, employment, housing quality, and income to rank neighborhoods by SES disadvantage; a higher quartile ADI equates to a greater disadvantage. Our data showed that patients in the lowest quartile ADI are 2.5 times more likely to have NGS testing compared to those in the highest quartile (OR: 2.54, 95% CI 1.07-6.20). These results suggest that NGS testing is disproportionately offered to insured patients with a higher SES, particularly those with insurance. Whether these discrepancies are inherent in clinical practice (e.g. physician awareness) or from legitimate barriers related to access should be defined in future studies. However, identifying that these disparities in NGS testing exists promotes awareness and encouragement for clinicians to offer NGS more broadly.

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