e18157 Background: Black women are more likely to die of breast cancer and develop more aggressive subtypes than white women. Black women are also more likely to be obese and have insulin resistance than white women. Insulin resistance has been associated with faster tumor growth but has not been studied as a potential mediator of racial disparities in women with breast cancer. We hypothesized that black women would present with more aggressive breast cancer and this would be associated with obesity and insulin resistance. Methods: We recruited 1017 (80% white, 20% black) women with new primary breast cancer, measured fasting blood glucose and insulin, body mass index (BMI), triple negative breast cancer (TNBC) & Nottingham prognostic index (NPI). We classified aggressive breast cancer as NPI > 4.4. We calculated insulin resistance scores (HOMA) and classified insulin resistance as HOMA > 2.8. Patients self-identified race. Results: Of 1017 women, average age was 58 years (SD = 12.0). 373 (37%) were stage 2+ at time of diagnosis; 19% had an NPI > 4.4. Black women presented with higher stage of cancer than white women (stage 2+: 45% vs 35%; p = 0.01), more TNBC than white women (10% vs 5%, p = 0.01), were more insulin resistant (24% vs 11%, p < .0001), had higher BMI (31.4kg/m2 vs 26.6 kg/m2; p < .0001) and NPI > 4.4 (29% vs. 17%, p = 0.0002) than white women. HOMA score was positively but not significantly associated with NPI score (r = 0.05; p = 0.1). Multivariate mediation regression model suggested that HOMA_IR does not mediate the effect from black race to higher NPI score (β = 0.01; 95%CI: -0.017 to 0.039). Conclusions: In women with newly diagnosed breast cancer, black women are more likely to be obese, have higher HOMA & NPI scores than white women. While these data are consistent with the hypothesized relationship of hyperinsulinemia promoting more aggressive breast cancer, to date, insulin resistance does not appear to mediate the effect of race and poor prognostic breast cancer.
Cytocompatibility of stabilized black phosphorus nanosheets tailored by directly conjugated polymeric micelles for human breast cancer therapy