Optimal Cut-Off Value for Detecting Breast Cancer-Related Lymphedema Using Ultrasonography

Background: We previously devised an ultrasonographic evaluation to calculate subcutaneous tissue cross-sectional area (△CSA). The reliability and accuracy of this method were demonstrated in healthy individuals and in patients with lymphedema. The purpose of this study was to estimate the optimal cut-off value of the ratio of the △CSA of the involved side (lesion side) to the contralateral side for detecting breast cancer-related lymphedema (BCRL) using ultrasonography. Methods and Results: Ultrasonographic measurements were performed 290 times in 150 patients. BCRL_D was defined as a confirmed difference of >2 cm in arm circumference. BCRL confirmed by a clinician (BCRL_C) was defined as the patient group that included not only BCRL_D but also patients with subcutaneous thickening and abnormal findings on lymphoscintigraphy, even if the difference in arm circumference was <2 cm. The △CSAs of both upper arms and forearms were calculated by measuring the thickness of the subcutaneous tissue at four locations using ultrasonography (superior, medial, inferior, lateral) at 10 cm above the elbow and 10 cm below the elbow. With a 1.35 △CSA ratio as the cut-off value for detecting BCRL_D, the sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were 0.88, 0.87, and 0.95, respectively. With a 1.20 △CSA ratio as the cut-off value for detecting BCRL_C, the sensitivity, specificity, and AUC were 0.92, 0.89, and 0.97, respectively. Conclusions: Our findings suggest that a 1.20 △CSA ratio as determined using ultrasonography, corresponding to a tape measurement of 1.05 cm, can be considered as a diagnostic criterion for lymphedema.