Very low mammographic breast density predicts poorer outcome in patients with invasive breast cancer

Objectives To examine the prognostic value of mammographic breast density (MBD) and mammographic features and their relationship with established prognostic factors in patients with invasive breast cancer. Methods Mammographic characteristics of 270 patients were analyzed. MBD was classified according to percentile density (<5 %, 5-10 %, 10-25 %, 25-50 %, 50-75 %, >75 %) and further categorized into very low density (VLD; <10 %), low density (LOD; <25 %) and mixed density (MID; >25 %). Mammographic features were compared with established prognostic factors and patient outcomes while correcting for possible confounders. Results MBD was inversely associated with tumour grade ( p = 0.019). Patients with LOD breasts had worse prognoses compared to those with MID breasts (disease-free survival 74.7 % vs. 84.8 %, p = 0.048; overall survival 75.3 % vs. 90.2 %, p = 0.003). Patients with VLD breasts showed the strongest significance compared to the remaining patients, even after adjusting for age, body mass index, and menopausal status. No other mammographic feature was prognostically significant. In Cox regression analysis, VLD proved to be an independent, poor prognostic feature (hazard ratio = 3.275; p < 0.001). Conclusion In patients with newly diagnosed breast cancer, very low MBD proved to be an independent prognostic feature, associated with higher tumour grade and predicted worse survival even after correcting for possible confounders. Key Points • Percentile mammographic breast density was associated with patient prognosis . • Very low density proved to be an independent poor prognostic factor . • Only patients with densities <10 % displayed this difference in survival . • Mammographic breast density was inversely associated with histological tumour grade .