Redefining the Diagnostic Threshold for Breast Cancer-related Lymphedema

Objective: To empirically determine a normative, distribution-based threshold for diagnosing breast cancer-related lymphedema (BCRL) and compare its diagnostic accuracy with the conventional 10% interlimb volume difference criterion. Summary Background Data: BCRL is a common and morbid sequela of breast cancer treatment; however, diagnostic thresholds remain inconsistent and inadequately validated. The widely used threshold of ≥10% interlimb volume difference may miss clinically relevant cases. Methods: This prospective cohort study analyzed preoperative bilateral limb measurements in 858 female breast cancer patients undergoing axillary surgery to derive a normative, distribution-based interlimb volume difference threshold. A threshold corresponding to 2 standard deviations (SD) above the mean (7.5%) was identified. Diagnostic performance of this proposed threshold was then compared with the conventional 10% cutoff in a subgroup of 167 patients who underwent axillary lymph node dissection (ALND) with up to 36 months of postoperative follow-up. Results: Among 858 patients (median [IQR] age, 48 [40-56] years; median BMI, 25.5 [22.3-30.0] kg/m²), preoperative interlimb volume differences were normally distributed (mean, 0.24%; SD, 3.74%), supporting a proposed diagnostic threshold of 7.5%. In the 167 patients who underwent ALND, 72 (43.1%) met the ≥7.5% threshold versus 53 (31.7%) meeting the 10% threshold, yielding 19 additional diagnoses (+11.4%; P <0.001). Of those meeting the 7.5% threshold, 94.4% (68/72) reported symptoms and/or used compression garments. Conclusions: A normative, distribution-based threshold of 7.5% interlimb volume difference improves the identification of clinically meaningful BCRL compared with the traditional 10% cutoff. Adopting this empirically validated threshold may enhance early detection, intervention, and patient outcomes.