Dosimetric Evaluation of Volumetric Modulated Arc Therapy (VMAT) for Left-Sided Breast Cancer Assessment of Plan Quality Using Conformity and Homogeneity Indices Using Monaco Treatment

Ayan Khalied Eidan; Jenan Hussien Taha; Ahmed Mohammed Jasim

doi:10.58709/niujhs.v12i1.2605

Ayan Khalied Eidan Department of physiology/ Medical Physics, College of Medicine, University of Al-Nahrain, Baghdad, Iraq
Jenan Hussien Taha Department of Physiology/ Medical Physics, College of Medicine, University of Al- Nahrain, Baghdad, Iraq
Ahmed Mohammed Jasim RT Board Certified Clinical Radiation Oncologist Iraqi Board Of Medical Specialities

DOI: https://doi.org/10.58709/niujhs.v12i1.2605

Abstract

Introduction: Radiotherapy serves as the main treatment approach for breast cancer on the left side. The challenge lies in ensuring sufficient coverage of the target while reducing radiation exposure to nearby organs at risk. Volumetric modulated arc therapy (VMAT) has been introduced to enhance dose conformity and better protect normal tissues.

Objective: This research aimed to assess the dosimetric properties of VMAT plans for patients with left-sided breast cancer by examining dose–volume histogram (DVH) parameters.

Methods: A retrospective analysis was conducted on fifty VMAT treatment plans. The dosimetric assessment focused on target coverage metrics (V95%, conformity index, and homogeneity index) and the radiation doses received by organs at risk, such as the heart, ipsilateral lung, contralateral lung, contralateral breast, esophagus, and spinal cord.

Results: VMAT planning provided consistent and clinically satisfactory dosimetric outcomes for both the target volumes and surrounding normal tissues. The chest wall PTV had an average V95 of 97.2%, while the lymph node PTV reached 98.7%, demonstrating sufficient target coverage with satisfactory conformity and dose uniformity. In terms of organs at risk, cardiac exposure was kept low, with the heart receiving an average dose of 5.0 Gy. The ipsilateral lung experienced mean V5, V20, and V30 values of 56.6%, 25.0%, and 21.0%, respectively. In contrast, the contralateral lung was subjected to minimal high-dose exposure, as indicated by mean V20 and V30 values of 0.3% and 0.06%. The contralateral breast received an average dose of 3.5 Gy, and the esophagus had a mean dose of 13.1 Gy, with a mean maximum dose of 33.6 Gy. Additionally, the spinal cord's mean maximum dose was 13.6 Gy. These dosimetric results suggest that VMAT effectively targeted irradiation while keeping radiation exposure to nearby critical structures within acceptable clinical thresholds.

Conclusion: VMAT achieved efficient target coverage, demonstrating good dose conformity and uniformity, all while keeping radiation exposure to nearby organs at risk within acceptable limits. These results endorse the clinical practicality of using VMAT for treating left-sided breast cancer.