A Prospective Study of Radiation Therapy After Immediate Lymphatic Reconstruction: Analysis of the Dosimetric Implications.

Axillary lymph node dissection (ALND) and regional nodal irradiation (RNI) are the primary causes of breast cancer-related lymphedema (BCRL). Immediate lymphatic reconstruction (ILR) is a novel surgical procedure that reduces the incidence of BCRL after ALND. The ILR anastomosis is placed in a location thought to be outside the standard radiation therapy fields to prevent radiation-induced fibrosis of the reconstructed vessels; however, there is excess risk of BCRL from RNI even after ILR. The purpose of this study was to understand the radiation dose distribution in relation to the ILR anastomosis. This prospective study included 13 patients treated with ALND/ILR from October 2020 to June 2022. A twirl clip deployed during surgery was used to identify the ILR anastomosis site during radiation treatment planning. All cases were planned using a 3D-conformal technique with opposed tangents and an obliqued supraclavicular (SCV) field. RNI deliberately targeted axillary Levels 1 to 3 and the SCV nodal region in 4 patients and was limited to Level 3 and SCV nodes in 9 patients. The ILR clip was located in Level 1 in 12 patients and Level 2 in 1 patient. In patients with radiation directed at only Level 3 and SCV, the ILR clip was still within the radiation field in 5 of these patients and received a median dose of 3939 cGy (range, 2025-4961 cGy). The median dose to the ILR clip was 3939 cGy (range, 139-4961 cGy) for the entire cohort. The median dose was 4275 cGy (range, 2025-4961 cGy) when the ILR clip was within any radiation field and 233 cGy (range, 139-280 cGy) when the clip was outside all fields. The ILR anastomosis was often directly irradiated with 3D-conformal techniques and received substantial radiation dose, even when the site was not deliberately targeted. Long-term analysis will help determine whether minimizing radiation dose to the anastomosis will decrease BCRL rates.

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