Optical imaging correlates with magnetic resonance imaging breast density and revealscomposition changes during neoadjuvant chemotherapy

In addition to being a risk factor for breast cancer, breast density has beenhypothesized to be a surrogate biomarker for predicting response toendocrine-based chemotherapies. The purpose of this study was to evaluate whethera noninvasive bedside scanner based on diffuse optical spectroscopic imaging(DOSI) provides quantitative metrics to measure and track changes in breast tissuecomposition and density. To access a broad range of densities in a limited patientpopulation, we performed optical measurements on the contralateral normal breastof patients before and during neoadjuvant chemotherapy (NAC). In this work, DOSIparameters, including tissue hemoglobin, water, and lipid concentrations, wereobtained and correlated with magnetic resonance imaging (MRI)-measuredfibroglandular tissue density. We evaluated how DOSI could be used to assessbreast density while gaining new insight into the impact of chemotherapy on breasttissue.

This was a retrospective study of 28 volunteers undergoing NAC treatment forbreast cancer. Both 3.0-T MRI and broadband DOSI (650 to 1,000 nm) were obtainedfrom the contralateral normal breast before and during NAC. Longitudinal DOSImeasurements were used to calculate breast tissue concentrations of oxygenated anddeoxygenated hemoglobin, water, and lipid. These values were compared withMRI-measured fibroglandular density before and during therapy.

Water (r = 0.843; P < 0.001), deoxyhemoglobin (r =0.785; P = 0.003), and lipid (r = -0.707; P = 0.010)concentration measured with DOSI correlated strongly with MRI-measured densitybefore therapy. Mean DOSI parameters differed significantly between pre- andpostmenopausal subjects at baseline (water, P < 0.001;deoxyhemoglobin, P = 0.024; lipid, P = 0.006). During NACtreatment measured at about 90 days, significant reductions were observed inoxyhemoglobin for pre- (-20.0%; 95% confidence interval (CI), -32.7 to -7.4) andpostmenopausal subjects (-20.1%; 95% CI, -31.4 to -8.8), and water concentrationfor premenopausal subjects (-11.9%; 95% CI, -17.1 to -6.7) compared with baseline.Lipid increased slightly in premenopausal subjects (3.8%; 95% CI, 1.1 to 6.5), andwater increased slightly in postmenopausal subjects (4.4%; 95% CI, 0.1 to 8.6).Percentage change in water at the end of therapy compared with baseline correlatedstrongly with percentage change in MRI-measured density (r = 0.864; P = 0.012).

DOSI functional measurements correlate with MRI fibroglandular density, bothbefore therapy and during NAC. Although from a limited patient dataset, theseresults suggest that DOSI may provide new functional indices of density based onhemoglobin and water that could be used at the bedside to assess response totherapy and evaluate disease risk.