Transillumination breast spectroscopy (TiBS): A potential tool to monitor changes in breast tissue composition during pregnancy and breast-feeding.

A21

A first full-term pregnancy and breastfeeding confers a major change in a woman's lifetime risk of developing breast cancer. The extent and direction of change depends primarily on the woman's age. Compositional and morphological changes in the breast tissue are mainly due to changes in the glandular structure (rapid cellular proliferation of type 1 and 2 lobules in the 2nd trimester followed by and differentiation of these lobules to type 3 and 4 near the end of pregnancy). Therefore, pregnancy and breastfeeding can be regarded as a model of risk reduction intervention. Near-infrared Transillumination Breast Spectroscopy (TiBS) uses light to access structural and metabolic bulk tissue properties, providing quantitative physical and physiological information. Here we aim to demonstrate TiBS's ability to identify, quantify and monitor tissue compositional changes during pregnancy and breastfeeding. Measurements were obtained from two groups of females between the ages 25 - 45 years (N = 55). The case group consists of women undergoing or recently completed a first full-term pregnancy (N = 14) and control group consists of nulliparous women (N = 41). Spectrally resolved transmitted light collected from 4 quadrants of both breast perpendicular to the cranial-caudal axis is detected. Principle component analysis (PCA) was used to reduce mean-centered spectral data and generate individual scores (tx), which differ as a function of physiologic and morphologic tissue composition. Changes in the scores are analyzed as a function of time in both groups and relative to the baseline (pre-pregnancy) measurements. Four principle components (p1 to p4) were identified accounting for 99.4% of the spectral variance. t1 and t3 show changes consistent with glandular structure proliferation and differentiation. t4 shows changes maybe related to the lactation process (increase lipid content due to milk production). t3 shows different trends of breast tissue changes between women younger and older than 35 years. Prospective TiBS data on women undergoing a first full-term pregnancy and breastfeeding may provide information relating to the magnitude of a short-term increased breast cancer risk due to the pregnancy and conversely the ability of TiBS to detect changes in tissue composition may make it a valuable tool to monitor efficacy of risk reduction interventions.