Abstract PS3-08-15: Prognostic Significance of Oncotype DX (RS) and MammaPrint (MP) in Post-Menopausal Estrogen Receptor-Positive (ER+), Node-Positive (N1) Breast Cancer (BC) patients: A Comparative Analysis by Race Using the National Cancer Database

Abstract Background: Postmenopausal ER+ patients often undergo genomic testing with RS or MP to assess chemotherapy benefits. However, the prognostic value of RS, particularly among ethnic minorities, remains unclear. Methods: We analyzed postmenopausal breast cancer patients (age > 50) from the 2022 NCDB with non-metastatic, ER+, HER2-negative, N1, T1-4 tumors who had undergone either RS or MP. They were categorized as African American (AA) or Caucasian (W). Associations of tumor and patient characteristics with race were assessed using Wilcoxon rank sum test and chi-square/Fisher’s exact tests. Kaplan-Meier estimates of 5-yr overall survival (OS) were determined for AA and W with respect to the results of MP and RS. Unadjusted and covariate adjusted hazard ratios (HR) were estimated with Cox proportional hazard regression to assess the association between race and OS. Subgroup analyses were conducted to explore disparities and trends. Results: 37,951 postmenopausal females were identified who met the above criteria, of whom 30,398 had RS<26 [W:27,889 (91.75%), AA: 2,509 (8.25%)], 1,982 had low risk MP [W: 1,802 (90.92%), AA: 180 (9.08%)], 4,459 had RS ≥26 [W: 3,970 (89.03%), AA: 489 (10.97%)] and 1,112 had high MP [W: 942 (84.71%), AA: 170 (15.29%)]. AA compared to W had higher rates of grade 3 disease in patients with RS<26 (13% vs 9.9%, p<0.001), RS ≥26 (53% vs 45%, p=0.014), while no difference in high MP (40% vs 37%, p=0.73) and had lower rates in low MP (6.9% vs 7.5%, p=0.011), though grade 2 rates were higher (73% vs 62%, p=0.011). Receipt of chemotherapy and endocrine therapy was similar in both races in all groups, except receipt of endocrine therapy in AA was less than W in high MP (89% vs 95%, p=0.006). Adjusted HRs showed no significant difference by race for high MP, RS ≥26, and low MP, while AA had almosta 15% increased risk of death compared to W if RS<26 [HR 1.149 (1.02-1.294), p=0.022]. Subgroup analysis of RS<26 showed that AA had increased risk of dying if Age ≤ 65 [HR 1.28(1.08-1.52)], grade 3 disease [HR 1.38 (1.05-1.82)], or had RS 11-25 [HR 1.23 (1.08-1.41)]. Conclusion: In patients with low-risk RS, AA had increased risk of death compared to W, while there was no difference for high-risk RS, low or high MP. Equal endocrine therapy and chemotherapy in low RS suggest no apparent gap in care, hence these findings point towards racial difference seen in prognostication between RS and MP. Further studies are needed to determine the validation of such prognostication tests across races. Citation Format: D. Desai, C. Widholm, P. Ashok Kumar, E. Hill, S. Sammons, A. Sivapiragasam. Prognostic Significance of Oncotype DX (RS) and MammaPrint (MP) in Post-Menopausal Estrogen Receptor-Positive (ER+), Node-Positive (N1) Breast Cancer (BC) patients: A Comparative Analysis by Race Using the National Cancer Database (NCDB) [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-08-15.