Applicability of Oncotype DX Testing in a Diverse Breast Cancer Population in Hawaii

Purpose: The Oncotype DX test is standardly used for patients with early-stage, hormone-receptor-positive, HER2-negative breast cancers to determine the benefit from chemotherapy and the likelihood of distant recurrence. The relationship between Oncotype DX recurrence scores and race/ethnicity is still being studied. This retrospective study aims to evaluate the relationship between Oncotype DX recurrence scores, race/ethnicity, and clinicopathological factors and to support the applicability of the Oncotype DX test for a diverse breast cancer population of Hawaii. Materials and Methods: We evaluated 879 breast cancer cases diagnosed from January 2018-March 2022 within a major health system in Hawaii, 600 of which received Oncotype DX recurrence scores to provide prognostic and therapy-predictive information based on NCCN guidelines. Linear regression with both univariable (unadjusted) and multivariable (adjusted for all other variables) models was run on the 600 breast cancer cases that received Oncotype DX recurrence scores. The predictor variables were age at diagnosis, race, tumor size, ER/PR status, and histology. Results: On multivariable analysis, we found statically significant differences in Oncotype DX recurrence scores according to age (60-69 vs. 18-49, p=0.01), ER/PR status (PR-positive vs. PR-negative, p < 0.0001), histology (other vs. ductal, p=0.004), and tumor size (2-5 cm vs. 0-1 cm, p=0.0003). We found no significant differences in Oncotype DX recurrence scores according to race/ethnicity. Conclusion: Our findings indicate that Oncotype DX recurrence scores are not variable according to race/ethnicity, highlighting the need for further research to understand the known disparities in breast cancer outcomes among different racial/ethnic groups. Our study supports the correlation between Oncotype DX recurrence scores and other factors and aligns with established prognostic trends for these variables in a diverse population. This study supports the applicability for the Oncotype DX test in a diverse breast cancer population of Hawaii.