Comparison of brachial plexus and critical organ doses with conformal, intensity modulated radiotherapy (IMRT) and volumetric arc therapy (VMAT) radiotherapy techniques in left breast cancer patients receiving locoregional radiotherapy

Introduction and Objective: In patients with breast cancer with lymph node involvement, postoperative locoregional radiation therapy has been proven to reduce the risk of locoregional recurrence and increase breast cancer survival.Locoregional radiotherapy may cause late toxicity (neuropathy) and edema in the brachial plexus.The effects of radiotherapy on adjacent non-target normal tissue were revised in 2010 under the title of QUANTEC.While the risk area is irradiated with a homogeneous dose distribution, the aim is for the normal tissue to receive minimum the least dose.Studies have shown that the occurrence of paresthesia increases after radiation therapy and that this effect is independent of the type of breast surgery, the number of axillary lymph nodes examined, and whether or not chemotherapy is received.Clinically, brachial plexopathy can manifest as neuropathic pain, paresthesias, or motor weakness in the upper extremities and may cause significant morbidity that will affect the quality of life of patients.In this study, we aimed to compare the dose amounts to be received by the brachial plexus and other critical organs (heart, lung, thyroid gland, medulla spinalis, esophagus and contralateral breast tissue) in left breast cancer patients receiving locoregional radiotherapy using conformal, intensity modulated radiotherapy (IMRT) and volumetric arc therapy (VMAT) techniques and to determine the most ideal technique.Not only will we share the results we will obtain from the study with the literature, but it will also guide and encourage us to use the technique that provides the least toxicity in terms of brachial plexopathy and other organ doses in patients who need to receive locoregional radiotherapy in line with the results we will obtain in our routine clinical practice. Materials and Methods:In this study, doses to the Brachial Plexus and other critical organs (OAR) were calculated while applying the same dose to the target volume (PTV) using 3BCRT, IMRT and VMAT radiotherapy planning techniques.All plans were optimized to ensure that OARs (brachial plexus, left lung, heart, LAD, medulla spinalis, contralateral breast, esophagus, thyroid) received minimum the least dose, and all plans were compared using the dose-volume histogram (DVH). Results: The IMRT and VMAT techniques provided a more homogeneous dose distribution compared to 3D-CRT. IMRT was identified as the most effective technique in sparing the brachial plexus, which is important for reducing the risk of neurological complications. VMAT yielded more favorable results in reducing doses to the contralateral breast and esophagus. Regarding the heart and lungs, both IMRT and VMAT delivered lower doses than 3D-CRT, suggesting a better safety profile for cardiopulmonary toxicity. Conclusion:IMRT stands out in minimizing radiation dose to the brachial plexus, while VMAT shows potential in reducing the risk of secondary malignancy and dysphagia by better sparing the contralateral breast and esophagus. Both modern techniques demonstrated superior organ-at-risk protection compared to conventional 3D-CRT. Personalized treatment planning based on patient-specific characteristics is essential to maximize treatment efficacy while preserving quality of life. Key Words: 3BRKT, IMRT, VMAT, breast cancer, brachial plexus