Examining a genomic test in predicting extended endocrine benefit and recurrence risk in a diverse breast cancer population.

e12526 Background: Extending adjuvant endocrine therapy (EET) beyond five years for early-stage hormone receptor-positive (HR+) breast cancer reduces late distant recurrence risk. The genomic test, Breast Cancer Index (BCI), has prognostic value and predicts the benefits of prolonged therapy, yet no studies have explored this testing in a diverse population. This study assesses late distant recurrence risk and predictive benefits of EET to better understand its relevance in a diverse early-stage HR+ breast cancer population. Methods: We analyzed patient demographics, clinical and pathologic characteristics, and BCI scores of 150 women in Hawaii with early-stage HR+ breast cancer, self-identifying as White, Filipino, Japanese, Native Hawaiian, or other. Tumor characteristics examined include size, grade, histology, lymph node, and ER/PR/HER2 receptor status. Logistic regression analyses used race, distant recurrence risk, and tumor features as predictor variables. BCI prediction of benefit and distant recurrence risk served as outcome variables. Results: Japanese patients had significantly lower odds of having a high risk for distant recurrence (OR = 0.02, p < 0.0001) compared to White. Other Asian PIs also showed reduced odds of high distant recurrence risk (OR = 0.07, p = 0.02), albeit to a lesser extent than Japanese. Patients with high distant recurrence risk had significantly greater odds of a score predicting benefit than those with low risk (OR = 5.03, p = 0.009). Racial or ethnic differences in predicting benefit with EET were not statistically significant. Conclusions: Results show no racial or ethnic differences in predicting the benefit of EET, strengthening BCI’s universal applicability in diverse women with early-stage HR+ breast cancer. Patients with higher distant recurrence risk were predicted to benefit from EET. This suggests potential variations in tumor features or other factors affecting distant recurrence risk among racial groups. Limitations include a relatively small sample size and lack of data from patients representing other racial groups. Future studies should expand the sample size and adjust for known breast cancer risk factors to better understand the racial and ethnic implications of BCI.