Patterns of temporal changes in tissue dielectric constant as indices of localized skin water changes in women treated for breast cancer: a pilot study.

BACKGROUND Our goal was to characterize temporal patterns of skin Tissue Dielectric Constant (TDC) as a foundation for possible TDC use to detect and quantify lymphedema. Although limb volumes and bioimpedance analysis (BIA) are used for this purpose, potential TDC-method advantages are that it can be done in about 10 seconds at any body site to depths from 0.5 to 5.0 mm below the epidermis. METHODS AND RESULTS TDC at forearm, biceps, axilla, and lateral thorax, and BIA values and arm volumes were measured in 80 women with breast cancer prior to surgery and in decreasing numbers at 3, 6, 12, 18, and 24 months post-surgery. Results show that TDC values, reflecting water content in the measurement volume, vary by site and depth but that at-risk/contralateral side ratio (A/C) is relatively independent of site and depth and is the preferred TDC parameter to detect tissue water changes over time in unilateral conditions. Among sites measured, lateral thorax, followed by forearm, appears most useful for TDC measurements with axilla least useful. Pre-surgery TDC inter-side values and A/C ratios showed no significant inter-side differences, suggesting that breast cancer presence per se did not alter tissue water status in this patient population. Sequential changes in TDC A/C ratios detected a greater number of patients who had inter-arm ratio increases exceeding 10% than were detected using BIA ratios. This may indicate a greater sensitivity to localized tissue water changes with the TDC-method. CONCLUSIONS TDC is a technically viable and potentially useful method to track skin water changes in persons treated for breast cancer.