Association between mammographic breast density and outcome in patients with unilateral invasive breast cancer receiving neoadjuvant chemotherapy

Purpose: To analyze the relationship between mammographic breast density and tumor response and outcome at follow-up, in terms of overall survival (OS) and disease-free survival (DFS), in patients with unilateral invasive breast cancer receiving neoadjuvant chemotherapy (NACT). Methods: A total of 228 women (mean age, 47.6 years ± 10 [SD]; range: 24–74 years) with invasive breast cancer who underwent NACT were included in this observational retrospective study. Clinical, radiological and histopatological data were retrieved. Categorization of breast density was performed by two radiologists in consensus on mammography acquired at the time of diagnosis according to BI-RADS categories. Association between density categories and tumor response was analyzed in the overall population and in subgroups defined by menopausal status, tumor phenotype and stage at diagnosis. Kaplan–Meier (KM) curves were used to estimate the OS and DFS probabilities. Subgroup analyses based on menopausal status and tumor phenotype were performed. Results: A total of 30 patients (13.2%) achieved pathological complete response (pCR). No association between density categories and pCR was found (P = 0.973), even at subgroups analysis. The median follow-up time was 92 months. Patients with dense breast showed the longest DFS (P = 0.0094), results confirmed in premenopausal patients (P = 0.0024) and in triple negative breast cancers (P = 0.0292). Density category did not show a statistically significant association with OS. Conclusion: Breast cancer patients receiving NACT with extremely dense breasts showed better DFS. No evidence of breast density as a predictive marker for complete pathological response or as a prognostic factor in terms of OS was found.