Dosimetric comparison of hybrid IMRT and different arc techniques VMAT after breast-conserving surgery for left-sided breast cancer.

Purpose: This study aimed to comprehensively compare the dosimetric characteristics of three different radiotherapy techniques-hybrid intensity-modulated radiotherapy (hy-IMRT), tangential volumetric-modulated arc therapy (t-VMAT), and continuous volumetric-modulated arc therapy (c-VMAT)-used after breast-conserving surgery for left-sided breast cancer in the target area and organs at risk (OARs) after breast-conserving surgery for left-sided breast cancer. This evaluation aims to provide a solid basis for individualized radiotherapy planning in clinical practice.

Methods: Twenty female patients who underwent breast-conserving surgery for left-sided breast cancer were retrospectively selected. These patients were treated with hy-IMRT, t-VMAT, or c-VMAT. The doses received by the target area and OARs were precisely evaluated. Additionally, the dose distribution in normal tissues and treatment time of the three radiotherapy plans were carefully compared.

Results: All three techniques could meet the target zone dose requirements. In the planning gross tumor volume (PGTV), the average dose of hy-IMRT was the highest. c-VMAT demonstrated the best homogeneity index (HI) and conformity index (CI). For the planning target volume (PTV), c-VMAT also showed outstanding performance in terms of homogeneity and conformity (p < 0.001). Regarding OAR doses, although there was no significant difference in the mean cardiac dose among the three techniques (p = 0.69), c-VMAT had lower values in cardiac V10 dose volume, mean coronary left anterior descending (LAD) artery dose, and V20, V30, and V40 dose volumes, irradiating less of the cardiac low-dose and high-dose regions. c-VMAT had lower left lung V30 and V40 doses, but its mean dose to the right lung was significantly higher than that of the other two groups. In terms of treatment time, t-VMAT was significantly shorter than the other two groups, indicating the highest efficiency (p < 0.001).

Conclusion: C-VMAT exhibits obvious advantages in target area uniformity, conformality, and protection of the heart and the affected lung. However, its significant dose impact on the right lung cannot be ignored and requires further attention. On the other hand, t-VMAT has a remarkable advantage in treatment time. This study offers valuable references for clinicians to select the most suitable radiotherapy technique according to patients' specific conditions, such as tumor location, size, and OAR anatomical structures, aiming to optimize treatment outcomes and minimize adverse effects.