The impact of race and glycemic control on triple negative breast cancer in type 2 diabetics

Abstract Although the association between type 2 diabetes (T2D) and breast cancer is well established, the relationship between glycemic control and breast cancer by hormone receptor subtype is poorly understood. We sought to investigate the relationship between glycemic control and the incidence of triple negative breast cancer (TNBC) among patients with T2D. Furthermore, we hoped to elucidate whether this hypothesized risk was further moderated by demographic factors, such as patient race. METHODS: A retrospective cohort study evaluating 1,679 patients with T2D diagnosed with breast cancer between 2010-2020 was conducted. Data including tumor hormone receptor status, Hgb A1c measured within 3 months of cancer diagnosis date, and patient race were ascertained via chart review. Tumor subtype was categorized as either hormone receptor-positive (ER+, PR+ or both) or triple-negative (ER/PR- and HER2/neu-). Based on Hgb A1c measurements, subjects were assigned to one of three categories of glycemic control: well-controlled (Hgb A1c less than 7.0), moderately controlled (Hgb A1c 7.0-9.4), or poorly controlled (Hgb A1c greater than or equal to 9.5) T2D. RESULTS: Accounting for all study subjects, the incidence of TNBC increased with worsening glycemic control (12.7% vs 15.2% vs 21.8%, P=0.040). Among non-Hispanic White patients, a significant increase in the incidence of TNBC with worsening glycemic control was also observed (9.2% vs 13.2% vs 21.9%, P=.010). Among Black patients, the incidence of TNBC did not significantly change across the three levels of glycemic control (17.6% vs 17.6% vs 22.7%, P=.700). Comparing the incidence rates of breast cancer by subtype between non-Hispanic White and Black patients across the three categories of glycemic control, a significant difference was only observed among patients with well-controlled T2D (17.6% of Black patients with TNBC versus 9.2% of non-Hispanic White patients, P<.001; 87.4% of non-Hispanic White patients with hormone receptor positive breast cancer versus 75.6% of Black patients, P<.001). CONCLUSION: Poor glycemic control is associated with a higher incidence of TNBC in patients with T2D overall. A significant increase in the incidence of TNBC with lesser degrees of glycemic control was only observed in the population of non-Hispanic white patients. Although previous studies have shown that Black patients are 2-3 times more likely to develop TNBC than their non-Hispanic White counterparts, a statistically significant racial difference in the rates of breast cancer by subtype was only noted among those with well-controlled T2D. Together our data not only suggests that T2D may serve as a modifiable risk factor for the development of TNBC, but also that the risk conferred by poor glycemic control may bear more significance for non-Hispanic White patients than Black patients. Citation Format: Madison E. Miller, Myah Bell, Priscella Holland, Vanessa Ibrahim, Gordon Jacobsen, Monique Swain. The impact of race and glycemic control on triple negative breast cancer in type 2 diabetics [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr A069.