Mammographic breast density and survival in women with invasive breast cancer

Purpose We explored the under-debate association between mammographic breast density (MBD) and survival. Methods From the Piedmont Cancer Registry, we identified 693 invasive breast cancer (BC) cases. We analyzed the overall survival in strata of MBD through the Kaplan-Meier method. Using the Cox proportional hazards model, we estimated the hazard ratios (HRs) of death; using the cause-specific hazards regression model, we estimated the HRs of BC-related and other causes of death. Models included term for Breast Imaging-Reporting and Data System (BI-RADS) MBD (categorized as BI-RADS 1 and BI-RADS 2-4) and were adjusted for selected patient and tumour characteristics. Results There were 102 deaths, of which 49 were from BC. After 5 years, the overall survival was 69% in BI-RADS 1 and 88% in BI-RADS 2-4 (p < 0.01). Compared to BI-RADS 2-4, the HRs of death for BI-RADS 1 were 1.65 (95% CI 1.06-2.58) in the crude model and 1.35 (95% CI 0.84-2.16) in the fully adjusted model. Compared to BI-RADS 2-4, the fully adjusted HRs for BI-RADS 1 were 1.52 (95% CI 0.74-3.13) for BC-related death and 1.83 (95% CI 0.84-4.00) for the other causes of death. Conclusion Higher MBD is one of the strongest independent risk factors for BC, but it seems not to have an unfavorable impact on survival.