Real-world patterns of Oncotype DX (O-Dx) testing and chemotherapy (CT) use among patients with early-stage, hormone receptor–positive (HR+) breast cancer (BC).

528 Background: O-Dx, a 21-gene assay, has transformed the management of patients with early-stage, HR+, HER2-negative (HER2-) BC by guiding personalized treatment decisions regarding adjuvant CT. However, real-world patterns of CT use based on recurrence score (RS) remain a topic of interest. Using a large, hospital-based database, we evaluated testing patterns, factors associated with O-Dx testing, and examined predictors of CT use among patients by RS. Methods: Patients ≥18 years with early-stage, HR+/HER2- BC diagnosed from 2018-2021 who underwent surgery and had pT1-T3, pN0-N1 disease were identified in the National Cancer Database. Descriptive analyses were used to compare baseline sociodemographic, clinical and treatment characteristics by receipt of O-Dx testing. Multivariable logistic regression was used to examine factors associated with receipt of O-Dx testing and predictors of CT use, stratified by RS into 0-10 (low risk), 11-25 (intermediate risk) and > 25 (high risk). Results: Of 319,771 patients with early-stage, HR+/HER2- BC, 54% (172,491) received O-Dx testing. Median age was 61 among those who received testing and 65 among those who did not. Black (aOR = 0.93; 95%CI 0.90–0.95) and Hispanic patients (aOR = 0.89; 95%CI 0.86–0.92) were less likely to receive testing than White patients. Compared to private insurance, those on Medicare (aOR = 0.93; 95%CI 0.91–0.95), Medicaid (aOR = 0.89; 95%CI 0.86–0.92), or no insurance (aOR = 0.91; 95%CI 0.85–0.98) had lower odds of O-Dx testing. While older age, higher comorbidity scores and pN1 disease were associated with lower odds of testing, recent year of diagnosis, pT2 disease, lobular histology, higher grade and treatment in academic facilities were linked to higher odds of testing. Overall, 16% (51,213) of patients received CT. Of those, 17.3% did not have an O-Dx test, while 76% of those who received CT and testing had RS > 25. 4.2% of patients aged 18-49 years received CT despite RS 0-10. Among patients without a test, being Black (aOR = 1.19; 95%CI 1.12–1.26) or Hispanic (aOR = 1.08; 95%CI 1.01–1.16) was associated with higher odds of receiving CT. Black patients with RS > 25 (aOR = 0.84; 95%CI 0.76–0.93) were less likely to receive CT than White patients. Larger tumors, pN1 disease and higher-grade tumors were associated with greater odds of CT receipt while older age at diagnosis and lobular histology were associated with lower odds regardless of RS. Conclusions: O-Dx testing has been increasingly incorporated into clinical practice. Our findings highlight disparities in the receipt of O-Dx testing and CT use, particularly according to RS. Black patients who did not undergo O-Dx testing were more likely to receive CT, while those with RS > 25 were less likely to receive CT. Further research is needed to explore physician and patient decision-making regarding O-Dx testing and adjuvant CT.