Breast Cancer in San Francisco: Disentangling Disparities at the Neighborhood Level.

Background: This study uses a novel geographic approach to summarize the distribution of breast cancer in San Francisco and aims to identify the neighborhoods and racial/ethnic groups that are disproportionately affected by this disease. Methods: Nine geographic groupings were newly defined on the basis of racial/ethnic composition and neighborhood socioeconomic status. Distribution of breast cancer cases from the Greater Bay Area Cancer Registry in these zones were examined. Multivariable logistic regression models were used to determine neighborhood associations with stage IIBthorn breast cancer at diagnosis. Cox proportional hazards regression was used to estimate the hazard ratios for all-cause and breast cancer-specific mortality. Results: A total of 5,595 invasive primary breast cancers were diagnosed between January 1, 2006 and December 31, 2015. We found neighborhood and racial/ethnic differences in stage of diagnosis, molecular subtype, survival, and mortality. Patients in the Southeast (Bayview/Hunter's Point) and Northeast (Downtown, Civic Center, Chinatown, Nob Hill, Western Addition) areas were more likely to have stage IIBthorn breast cancer at diagnosis, and those in the East (North Beach, Financial District, South of Market, Mission Bay, PotreroHill) and Southeast were more likely to be diagnosed with triple-negative breast cancers (TNBC). Compared with other racial/ethnic groups, Blacks/African Americans (B/AA) experienced the greatest disparities in breast cancer-related outcomes across geographic areas. Conclusions: San Francisco neighborhoods with lower socioeconomic status and larger minority populations experience worse breast cancer outcomes. Impact: Our findings, which reveal breast cancer disparities at sub-county geographic levels, have implications for population-level health interventions.