Background: Early diagnosis and treatment of breast cancer-related arm lymphedema (BCRAL) is essential to prevent progression. Local tissue water (LTW) can be assessed using the tissue dielectric constant (TDC), enabling detection before an increase of arm volume occurs. However, knowledge of the variation of LTW during cancer treatment and appropriate LTW thresholds for early detection of BCRAL is limited. The aim of this study was to examine differences in LTW between the arms, assess changes in LTW in each arm during adjuvant treatment, and calculate theoretical inter-arm thresholds for BCRAL. Method and Results: This retrospective cohort study included 120 women treated with axillary lymph node dissection and radiotherapy. At 4–6 weeks post-surgery, LTW was significantly higher in the contralateral upper arm and the forearm at the lateral site compared to the ipsilateral arm. At 3–4 months post-radiotherapy, LTW remained higher in the contralateral upper arm at the lateral site and the forearm at the medial site. LTW decreased at the medial site of the ipsilateral upper arm and at the ventral site of the contralateral upper arm. Potential TDC ratio thresholds to detect BCRAL, including 3 SD, were calculated as 1.40 in the upper arm and 1.30 in the forearm. Conclusion: At both follow-ups, LTW was higher in the contralateral arm at specific sites compared to the ipsilateral arm and decreased at specific sites in both arms during oncological treatment. The calculated TDC thresholds may improve detection of BCRAL and enhance the interpretation of lymphedema status during oncological treatment.
Blom et al. (2026) studied this question.