The Role of Residential Segregation in Treatment and Outcomes of Ductal Carcinoma In Situ of the Breast.

BACKGROUND

It remains unclear whether residential segregation impacts on clinical treatment and outcomes for ductal carcinoma in situ (DCIS), a nonobligate precursor to invasive breast cancer (IBC).

METHODS

This population-based retrospective cohort study included adult non-Hispanic White and Black women diagnosed with unilateral DCIS between January 1990 and December 2015, followed through December 2016, and identified from the Surveillance, Epidemiology, and End Results dataset. County-level racialized economic segregation was measured using the Index of Concentration at the Extremes. Multilevel logistic regression and Cox proportional hazards regression accounting for county-level clustering were used to estimate the ORs of local treatment and HRs of subsequent IBC and mortality.

RESULTS

Of 103,898 cases, mean age was 59.5 years, 12.5% were non-Hispanic Black, 87.5% were non-Hispanic White, 97.5% underwent surgery, 64.5% received radiotherapy following breast-conserving surgery (BCS), 7.1% developed IBC, and 18.6% died from all causes. Among women living in the least versus most privileged counties, we observed higher odds of receiving mastectomy [vs. BCS; OR = 1.51; 95% confidence interval (CI), 1.35-1.69; Ptrend < 0.001] and radiotherapy following BCS(OR = 1.27; 95% CI, 1.07-1.51; Ptrend < 0.01); the risk was higher in subsequent ipsilateral IBC (HR = 1.16; 95% CI, 1.02-1.32; Ptrend = 0.04), not in breast cancer-specific mortality (HR = 1.04; 95% CI, 0.88-1.23; Ptrend = 0.56).

CONCLUSIONS

The results provide evidence for disparities in clinical treatment for DCIS and prognostic outcomes among women in racially and economically segregated counties.

IMPACT

Our findings may inform geographically targeted multilevel interventions to reduce breast cancer burden and improve breast cancer care and equity.