Identifying the Axillary Substructure at Risk for Lymphedema in Operable Patients With Breast Cancer Receiving Regional Nodal Irradiation

PURPOSE: Axillary substructures may contribute to the development of breast cancer-related lymphedema (BCRL). This study aimed to compare dose-volume parameters of various substructures to identify high-risk regions associated with BCRL and to evaluate the clinical applicability of these findings. METHODS AND MATERIALS: Cohort-Initial included 336 patients with pT1-3N0-1M0 breast cancer who underwent mastectomy or lumpectomy with axillary lymph node dissection (ALND) and regional nodal irradiation (RNI) between August 2018 and February 2021. The Norman questionnaire was used to assess BCRL. Thirteen dose-volume parameters across 8 axillary substructures were assessed for association with BCRL. Cohort-Recurrence comprised 50 consecutive ALND-treated patients with regional nodal recurrence diagnosed using positron emission tomography/computed tomography, used to evaluate the recurrence risk in the candidate substructures. Cohort-Reoptimization involved 20 patients from the Cohort-Initial who received excessive radiation doses in the candidate substructure. Their treatment plans were reoptimized to assess the feasibility of dose reduction while maintaining target coverage and organ dose. RESULTS: was feasible without compromising the radiation therapy plan quality. CONCLUSIONS: < 79.2% may serve as a recommended dose constraint for patients undergoing RNI after ALND. Avoiding excessive radiation to the ALTJ is clinically feasible and safe, potentially mitigating BCRL risk without compromising dose coverage to high-risk nodal regions.