RESUMO
BACKGROUND: This study aims to evaluate the relation between mammographic breast density (BD) and pathological response to neoadjuvant chemotherapy. METHODS: In this retrospective study, 241 breast cancer patients who received neoadjuvant chemotherapy were included. BD was assessed in mammograms already performed at diagnosis. Pathological complete response (pCR) and pathological stage were correlated with BD, tumour phenotype and other clinico-pathological factors. RESULTS: Patients with low BD had better pCR compared to those with high density (30.5% vs 19.5% respectively, OR = 1.8, 95% CI = 0.98-3.3, p = 0.056) which was more pronounced after adjustment with body mass index (BMI) (OR = 2.4, 95% CI = 1.2-4.8, p = 0.011). HER2-positive disease (32.5% vs. 18.4%, OR = 2.2, 95% = 1.2-4.0, p = 0.01), lower BMI (OR = 1.1, 95% CI = 1.03-1.15, p = 0.004) and lower clinical stage (p = 0.002) were significant predictors of pCR in univariate analysis. In multivariate analysis, low BD (OR = 2.7, 95% CI = 1.3-5.5, p = 0.006) and lower BMI (OR = 1.1, 95% CI = 1.03-1.17, p = 0.003) were independent predictors of better pCR, while early clinical stage (I, II) was of borderline significance (OR = 2.6, 95% CI = 0.99-6.7, p = 0.052). High BD (OR = 1.8, 95% CI = 1.1-3.2, p = 0.03), advanced clinical stage (III) (OR = 1.5, 95% CI = 1.03-2.1, p = 0.03) and higher BMI (OR = 1.06, 95% CI = 1.02-1.11, p = 0.006) were significant predictors of advanced pathological stage. CONCLUSION: Low mammographic BD, low BMI and early clinical stage were associated with improved pCR rate and lower pathological stage after neoadjuvant chemotherapy. BD had more pronounced association with response to chemotherapy after adjustment with BMI.