Socioeconomic- and insurance-based inequities in Oncotype DX testing and score-guided treatment.

1589 Background: 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 an early-stage, HR+/HER2- breast cancer from 2011-2023 within the nationwide Flatiron Health electronic health record-derived deidentified database. Socioeconomic status was measured by the Yost index, a census block-level measure of neighborhood deprivation. Insurance status was captured at time of diagnosis. Utilization of ODX testing was compared descriptively. Likelihood of receiving adjuvant chemotherapy by neighborhood deprivation or insurance status was estimated using relative risk, predicted probabilities, and 95% confidence intervals from adjusted Poisson models with robust variance estimates. Analyses were stratified by age due to differing recurrence risk score categorizations. ODX scores indicating low or low/medium recurrence risk suggests chemotherapeutic benefit will likely not outweigh risk of side effects, while scores indicating medium or high recurrence risk suggests chemotherapeutic benefit will likely outweigh risk of side effects. Results: Of 4,367 patients eligible for ODX testing, mean diagnosis age was 62 years (SD 12), 77% were white, 69% had stage I cancer, 8% had ≥1 comorbidity, 48% were commercially insured, and 30% lived in a highly deprived neighborhood. Compared to those without, patients with an ODX test (46%, n = 2,026) were more often white (81% vs. 74%), commercially insured (51% vs. 45%), or lived in a neighborhood of low deprivation (73% vs. 67%). For patients aged ≤50 with ODX testing (n = 370), 51%, 25%, 12%, and 12% had low, low/medium, medium, and high recurrence risk. Of those with low recurrence risk, patients who resided in neighborhoods of low vs. high deprivation had 9% higher probability of receiving potentially inappropriate overtreatment with adjuvant chemotherapy (15%, 95% CI 10-25% vs. 6%, 95% CI 2-24%). Of those with low/medium recurrence risk, publicly vs. commercially insured patients were 2.7x more likely to receive adjuvant chemotherapy (RR 2.71, 95% CI 1.00-7.39). For patients aged > 50 with ODX testing (n = 1,656), 83% and 17% had low and high recurrence risk. Of those with high recurrence risk, patients who resided in neighborhoods of high vs. low deprivation were 18% less likely to receive recommended adjuvant chemotherapy, suggesting undertreatment (RR 0.82, 95% CI 0.67-1.00). Conclusions: Socioeconomic- and insurance-based inequities, including both overtreatment and undertreatment, were observed in this national cohort of women with early stage breast cancer eligible for ODX testing, indicating opportunities to increase care quality.