Experimental and Analytical Comparisons of Tissue Dielectric Constant (TDC) and Bioimpedance Spectroscopy (BIS) in Assessment of Early Arm Lymphedema in Breast Cancer Patients after Axillary Surgery and Radiotherapy.

Tapani Lahtinen, Jan Seppa¨la¨, 1 Tuomas Viren, Karin Johansson. Lymphatic Research and Biology Volume 13, Number 3, 2015

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Experimental and Analytical Comparisons of Tissue Dielectric Constant (TDC) and Bioimpedance Spectroscopy (BIS) in Assessment of Early Arm Lymphedema in Breast Cancer Patients after Axillary Surgery and Radiotherapy.

Tapani Lahtinen, Jan Seppa¨la¨, 1 Tuomas Viren, Karin Johansson. Lymphatic Research and Biology Volume 13, Number 3, 2015

Background: Early diagnosis of breast cancer treatment-related lymphedema (BCRL) is of great importance for longstanding treatment results. Tissue dielectric constant (TDC) and bioimpedance spectroscopy (BIS) both have a potential for early diagnosis, but have not been compared.

Methods and Results: One hundred women, treated for breast cancer with breast surgery, axillary dissection, and radiotherapy, were examined within one year after breast cancer treatment, as part of the follow-up procedure. Affected/at-risk and contralateral arms were measured with the TDC technique specific to localized skin water content and the BIS technique assessing arm extracellular fluid (ECF). Thirty-eight patients were clinically diagnosed for lymphedema (38.0%). The sensitivity and specificity for the TDC method were 65.8% and 83.9%, and for BIS method 42.1% and 93.5%, (p<0.001 and NS), respectively. Of all lymphedema, 18.4% were detected only by TDC and 2.6% by BIS. Affected arm to contralateral arm TDC ratios for upper arm and forearm, 1.56–0.49 and 1.28–0.33, demonstrating the localized feature of the TDC measurements were significantly greater than the BIS arm ratio 1.12–0.12 (both p<0.001). Conclusions: Discrepancies between TDC and BIS techniques in assessing lymphedema are related to different measurement techniques and assessed tissue water components. Independently of selected technique-specific threshold limit, the TDC technique was more sensitive than the BIS technique in the early assessment of BCRL and demonstrated that nearly 20% of early lymphedema are only superficially localized. The results further supported the complementary role of TDC and arm volume measurements as a highly diagnostic method for early lymphedema

Main findings

  • One hundred women treated for breast cancer with surgery including axillary lymph node dissection (ALND) and radiotherapy to the breast and axilla were included in the study.
  • In the tissue dielectric technique (TDC), localized tissue water in the skin where early swelling in lymphedema is thought to exist was measured. The TDC skin water measurements were best aiding the diagnosis and localization of early lymphedema and also detected a number of non-lymphedematous patients potentially at risk for later occurrence of lymphedema compared with bioimpedance (BIS).
  • Results from the BIS technique were not correlating well with TDC technique in the assessment of patients with or without lymphedema.
  • Based on the resistance values of each tissue component it can be calculated that with BIS 76.5% of the total electric current flows through the muscle component and 9.9, 1.5, 4.5, and 7.6% through skin, subcutis, bone, and blood components, respectively. According to model calculations for an increase of 20% in skin tissue water, the total resistance changes less than 2.5%. This indicates that such a 20% change in skin water would be essentially undetectable with multi-frequency BIS analyzers.
  • Using the same model it can be shown that for an increase of 20% in skin tissue water the arm volume changes less than 2% (i.e., such a 20% change in skin water volume is practically undetectable by arm volume measurement).
  • The authors state calculations based on this simple, but representative model, suggests that the main route of electric current in the BIS technique is through the well-conducting (subfascial) muscle component that is largely spared of swelling and to a lesser amount through the skin where early lymphedema is thought to manifest.
  • The TDC ratio in lymphedema patients in the affected arm with respect to the contralateral arm was significantly greater in upper arm 1.56–0.49 than in forearm 1.28–0.33 (representing oedema of 56% and 28%, respectively) (Fig. 2).The observation of the greater oedema in upper arm skin might be related to dermal backflow.