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Several studies have demonstrated that hormone-blocking therapies are more effective at reducing breast cancer risk in women who exhibit >10% reduction in breast density compared to women who had little or no density change, suggesting that breast density is a predictor of tamoxifen effectiveness. The goal of this prospective study was to assess whether diffuse optical spectroscopic imaging (DOSI) can measure the changes in breast composition under adjuvant tamoxifen treatment for breast cancer.
The primary aim was to determine whether the change in the DOSI measurement of water correlates with the change in the MRI-derived quantitative measurement of breast density after 18 months of treatment in the contralateral normal breast of subjects receiving tamoxifen. Pre-menopausal subjects receiving tamoxifen (N=11 total, N=9 analyzable) and controls (N=18 total, N=15 analyzable) were enrolled and measured with co-registered DOSI and non-contrast MRI before, and 6, 12 and 18 months after beginning tamoxifen. Across all subjects, baseline MRI fibroglandular density correlated strongly with DOSI water (r=0.86, p<0.001), moderately with lipid (r=-0.63, p=0.001), and weakly with oxyhemoglobin (r=0.55, p=0.005) and deoxyhemoglobin (r=0.42, p=0.040) concentrations. Generalized estimating equation analysis revealed significant longitudinal differences between treated subjects and controls in the percentage change of MRI fibroglandular density (at 6 and 12 mo. timepoints), DOSI water (12 and 18 mo.), DOSI lipid (6, 12 and 18 mo.) Overall the data suggest that DOSI is sensitive to tamoxifen-induced changes in the human breast, and should be investigated further as a low-cost and low-risk means to predict response to tamoxifen treatment.
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