Association of Insulin Resistance and Higher Oncotype DX™ Recurrence Score

Background Black women with breast cancer have a worse overall survival compared with White women; however, no difference in Oncotype DX (TM) (ODX) recurrence scores has been observed to explain this health disparity. Black women are also disproportionately affected by insulin resistance. We evaluated whether insulin resistance is associated with a higher ODX recurrence score and whether there is a difference between White and Black women to explain disparate clinical outcomes. Methods A subgroup analysis of patients in a multi-institutional cross-sectional study evaluating differences in insulin resistance between White and Black women was performed. Women diagnosed with a new hormone receptor-positive, HER2/neu-negative breast cancer with an ODX recurrence score were identified. Fasting blood glucose and insulin measurements were used to calculate the homeostatic model assessment of insulin resistance (HOMA-IR) score, a method for assessing insulin resistance, and compared against ODX scores. Results Overall, 412 women (358 White women, 54 Black women) were identified. Compared with White women, Black women had a higher body mass index (30 vs. 26 kg/m(2), p < 0.0001), higher HOMA-IR score (2.4 vs. 1.4, p = 0.004), and more high-grade tumors (30% vs. 16%, p = 0.01). There was a direct positive association with an increasing ODX score and HOMA-IR (p = 0.014). On subset analysis, this relationship was seen in White women (p = 0.005), but not in Black women (p = 0.55). Conclusion In women with newly diagnosed breast cancer, increasing insulin resistance is associated with a higher recurrence score; however, this association was not present in Black women. This lack of association may be due to the small number of Black women in the cohort, or possibly a reflection of a different biological disease process of the patient's tumor.

Automated summary

Black women with breast cancer have higher body mass index and insulin resistance scores compared to White women, but their ODX recurrence scores do not correspondingly increase. This suggests that insulin resistance may be associated with breast cancer recurrence scores, but its impact may differ for Black women.