Comparison of volume displacement versus circumferential arm measurements for lymphoedema: Implications for the SNAC Trial

Abstract

Background: The Royal Australasian College of Surgeons Sentinel Node versus Axillary Clearance trial is a randomized controlled trial comparing sentinel node biopsy with axillary clearance in breast cancer patients. Primary study end-points include arm volume differences with time, which may indicate the development of lymphoedema. The RACS SNAC trial uses circumferential arm measurements in the estimation of arm volume. This study aimed to assess the accuracy of circumferential volume estimation in comparison with water displacement. Methods: Eighty-seven women attending the breast clinic at the Women's Health Centre, Royal Adelaide Hospital, were assessed by volumetric and circumferential arm measurements. Correlations between volume estimations and measurements were made, taking into account the width of measuring tape and body mass index. Results: There was a highly significant correlation between circumferential and volumetric arm measurements (Pearson's correlation coefficient = 0.92, P < 0.0001), especially when using the narrow measuring tape. Correlation was best in the overweight BMI group (Pearson's correlation coefficient = 0.94. P < 0.0001) and worst in the obese group (Pearson's correlation coefficient = 0.79, P < 0.0001) but all relationships were statistically significant. Conclusion: Using a narrow tape, circumferential arm measurement is an appropriate method for assessing arm volume in the SNAC trial.