Abstract
PURPOSE: Regional nodal irradiation (RNI) increases breast cancer-related lymphedema (BCRL) following axillary lymph node dissection despite immediate lymphatic reconstruction (ILR). This study examines the relationship between radiation (RT) dose to the ILR anastomosis and BCRL.
METHODS AND MATERIALS: This prospective study included 23 patients with invasive breast cancer who underwent axillary lymph node dissection/ILR followed by RNI. The anastomosis was indicated by a twirl clip, allowing for ILR contouring. The median RNI dose was 4000 cGy in 16 fractions. Lymphedema was defined as an increase in arm volume (10% dominant, 7% nondominant) in the affected extremity or a 10-point increase in Lymphedema Index plus patient-reported symptoms >6 months after RT completion. Dosimetric parameters included mean and maximum doses, V35, V40, Dmin<36.8Gy at the ILR site, ILR + 5 mm, and ILR + 2 cm expansion volumes.
RESULTS: Median follow-up was 25.9 months (interquartile range, 22.8-33.9). Fourteen patients met criteria for lymphedema at >1 time point, but only 4 (17.4%) met criteria for BCRL at their last follow-up. Patients who developed lymphedema had higher mean dose (4135 cGy vs 1410 cGy; P = .006), V35 (89% vs 20%; P = .005), and V40 (84% vs 17%; P = .012) at the ILR + 2 cm volume compared with those who did not. These parameters remained significant after controlling for BMI and the number of nodes removed. Threshold doses for lymphedema risk were found for the ILR + 2 cm volume: mean dose, 3074 cGy (AUC = 0.86), with rates of lymphedema above and below the threshold at 92% versus 30%, P = .006; V35, 56% (AUC = 0.87), 92% versus 22%, P = .001; and V40, 50% (AUC = 0.83), 92% versus 30%, P = .006.
CONCLUSIONS: Increasing RT doses to the ILR anastomosis site and the surrounding area increased lymphedema risk. Future studies will assess whether limiting the dose below these thresholds can lower BCRL rates while maintaining disease control.