Factors affecting the preoperative and postoperative extracellular fluid in the arm on the side of breast cancer: a cohort study.

BACKGROUND: To explore what factors affect volume of extracellular fluid (ECF) in the arm on the side of surgery pre- and postoperatively and to determine the value of knowing preoperative ECF volume for diagnosis of lymphedema postoperatively. METHODS AND RESULTS: Women (N=516) with early breast cancer were assessed preoperatively and within 4 weeks postoperatively. Baseline measures included inter-arm ECF ratio, side of cancer, number of nodes involved, and other individual characteristics. Postoperative assessment included inter-limb ECF ratio and details from surgery. The postoperative ECF ratio was categorized as to whether it exceeded previously established thresholds, and the change in ECF was categorized as to whether it exceeded 0.1. Linear regression identified which factors explained the variance for preoperative ECF ratio and the change in ratio. Chi square analysis compared whether women categorized using thresholds were the same as those whose ratio increased >0.1 postoperatively. Postoperative ECF ratio was significantly higher than the preoperative ratio (p<0.001). Women whose ECF ratio exceeded previously established thresholds were not the same as those whose ratio increased >0.1 postoperatively (p<0.001). Only the side of surgery explained the preoperative ECF measure; extent of surgery and actual weight explained the change in ECF ratio. CONCLUSION: The ECF ratio preoperatively is not affected by nodal involvement. The change in ECF ratio is affected by the extent of surgery and body mass. Change from preoperative ECF ratio did identify more women at risk for lymphedema than reliance postoperatively on thresholds, supporting preoperative measures.