Comparison of radiotherapy plans for grade II brain tumor patients created with two different treatment planning systems

Background and Aim: In radiotherapy, linear accelerator devices of different brands and models are commonly used, each integrated with its own treatment planning system. These systems employ various algorithms to generate patient-specific dose distributions. The performance of treatment planning systems may vary depending on their algorithms, optimization criteria, and technical specifications. Although there are several studies in the literature comparing different treatment planning system's dosimetrically, most are limited to specific tumor types or anatomical regions. The aim of this study is to compare radiotherapy plans created with two different treatment planning systems (Eclipse and Monaco) for patients diagnosed with grade II brain tumors, to identify any differences between them, and to offer clinical recommendations based on the findings. Material and Methods: Patients with a pathological diagnosis of grade II brain tumors were retrospectively selected for the study. Those with tumor sizes ranging between 2 and 6 cm were included. For each patient, radiotherapy plans were created using both the Eclipse (Varian) and Monaco (Elekta) treatment planning systems. Comparable optimization criteria (cost functions) were used to ensure the validity of the comparison. In both systems, it was ensured that at least 95% of the planning target volume received at least 95% of the prescribed dose. Critical organ doses and dose homogeneity were also evaluated and included in the analysis. Results: In the comparison, plans created with the Eclipse treatment planning system showed lower values for maximum dose, right and left lens maximum doses, left optic nerve maximum dose, brainstem maximum dose, and optic chiasm maximum dose compared to Monaco plans. Additionally, Eclipse plans exhibited more homogeneous dose distributions and shorter beam-on times. On the other hand, Monaco plans resulted in higher minimum doses to the and required fewer monitor units, indicating a potentially more efficient delivery. Conclusion: The findings demonstrate significant dosimetric differences between the two treatment planning systems. Eclipse treatment planning system stands out with its advantages in critical organ sparing, dose homogeneity, and shorter treatment times. In contrast, Monaco treatment planning system provides superior results in terms of lower monitor unit usage and higher minimum doses. In clinical decision-making, the proximity of the tumor to critical structures should be considered when selecting the appropriate treatment planning system. Eclipse may be more suitable for tumors located near critical organs, while Monaco could be preferred for more distant lesions. Keywords: brain tumors, treatment planning system, linear accelerator