Breast cancer staging by subtype in the Lower Mississippi Delta region States

Introduction: To evaluate disparities in breast cancer stage by subtype (categorizations of breast cancer based upon molecular characteristics) in the Delta Regional Authority (Delta), an impoverished region across eight Lower Mississippi Delta Region (LMDR) states with a high proportion of Black residents and high breast cancer mortality rates. Methods: We used population-based cancer registry data from seven of the eight LMDR states to explore breast cancer staging (early and late) differences by subtype between the Delta and non-Delta in the LMDR and between White and Black women within the Delta. Age-adjusted incidence rates and rate ratios were calculated to examine regional and racial differences. Multilevel negative binomial regression models were constructed to evaluate how individual-level and area-level factors affect rates of early- and late-stage breast cancers by subtype. Results: For all subtypes combined, there were no Delta/non-Delta differences in early and late stage breast cancers. Delta women had lower rates of hormone-receptor (HR + )/human epidermal growth factor 2 (HER2-) and higher rates of HR-/HER2- (the most aggressive subtype) early and late stage cancers, respectively, but these elevated rates were attenuated in multilevel models. Within the Delta, Black women had higher rates of late-stage breast cancer than White women for most subtypes; elevated late-stage rates of all subtypes combined remained in Black women in multilevel analysis (RR = 1.10; 95% CI = 1.04-1.15). Conclusions: Black women in the Delta had higher rates of late-stage cancers across subtypes. Culturally competent interventions targeting risk-appropriate screening modalities should be scaled up in the Delta to improve early detection.