Socioeconomic- and Insurance-Based Inequities in Oncotype DX Testing and Score-Guided Treatment.

PURPOSE: Personalized approaches to breast cancer treatment are increasingly guided by expensive, lab-based genomic testing like Oncotype DX (ODX) Breast Recurrence Score Test. Little is known about how socioeconomic and insurance status may affect utilization of ODX testing and subsequent ODX score-guided treatment. METHODS: This retrospective cohort study included women diagnosed with early-stage, HR+/HER2- breast cancer from 2011 to 2023 within the US-based, electronic health record (EHR)-derived, deidentified Flatiron Health Research Database. Socioeconomic status was measured by a census block-level measure of neighborhood deprivation. Insurance status was captured at the time of diagnosis. Utilization of ODX testing was compared descriptively. Age-stratified likelihood of adjuvant chemotherapy by neighborhood deprivation or insurance status was estimated using relative risk, predicted probabilities, and 95% confidence intervals from adjusted Poisson models. RESULTS: Of 3814 patients eligible for ODX testing, 47% were commercially insured, and 31% lived in an impoverished neighborhood. Compared to those without, patients with an ODX test (47%, n = 1797) were more often white (81% vs. 74%), commercially insured (50% vs. 44%), or lived in an affluent neighborhood (72% vs. 66%). For patients aged ≤ 50 with low recurrence risk, patients who resided in affluent vs. impoverished neighborhoods had a 5% higher probability of receiving potentially inappropriate overtreatment with adjuvant chemotherapy. Of those with low/medium recurrence risk, publicly insured patients had more than double the probability of receiving adjuvant chemotherapy compared to those privately insured, suggesting potential overtreatment. For patients aged > 50 with ODX with high recurrence risk, Medicare beneficiaries had a 5% lower probability than privately insured patients and an 11% lower probability than Medicaid/Other beneficiaries of receiving recommended adjuvant chemotherapy, suggesting under treatment. CONCLUSION: Socioeconomic- and insurance-based inequities, including both overtreatment and undertreatment, were observed in this EHR-based cohort of women with early-stage breast cancer eligible for ODX testing, indicating opportunities to increase care quality.