Effect of neoadjuvant chemotherapy on breast tissue composition: a longitudinal mammographic study with automated volumetric measurement.

OBJECTIVES: To investigate the effect of neoadjuvant chemotherapy (NAC) on breast tissue composition with mammographic automated volumetric measurement. METHODS: This retrospective study included 168 breast cancer patients who were treated with NAC and underwent serial mammography (pre-treatment, mid-treatment, and post-treatment) between January 2015 and October 2018. Automated volumetric measurements of the contralateral breast volume (BV), fibroglandular volume (FGV), and breast density (BD) were performed using Volpara software. BD grades were divided into 4 groups by Volpara density grade (VDG). The longitudinal changes in BV, FGV, BD, and their associated factors were evaluated. RESULTS: Repeated-measures analysis of variance demonstrated a significant reduction in BV, FGV, and BD over time (p < 0.001, p < 0.001, and p = 0.002, respectively). BV showed a greater reduction in the second half than in the first half (- 28.6 cm(3) vs. - 15.2 cm(3)), BD showed a greater reduction in the first half than in the second half (- 0.8% vs. - 0.1%), and FGV steadily decreased (- 4.6 cm(3) and - 3.9 cm(3) in the first and second halves). On multivariable linear regression analysis, chemotherapy regimen was associated with BV change between pre- and post-treatment (p = 0.002); age (p = 0.024) and VDG (p = 0.027) were associated with FGV change; age (p = 0.037), VDG (p = 0.002), and chemotherapy regimen (p = 0.003) were associated with BD change. CONCLUSIONS: NAC affects breast tissue composition, reflected as reductions in BV, FGV, and BD. Mammography with automated volumetric measurement can capture quantitative changes in these breast tissue parameters during NAC. KEY POINTS: * Neoadjuvant chemotherapy (NAC) affects breast tissue composition with different patterns of reduction in breast volume, fibroglandular volume, and breast density. * Age, Volpara density grades, and NAC regimen were independent factors associated with breast density change between pre-treatment and post-treatment. * Mammography with automated volumetric measurement enables identification of longitudinal changes in breast tissue composition.