| Abstract [eng] |
Globally, lung cancer remains one of the most common causes of cancer occurrence and mortality. Stereotactic body radiation therapy has grown in importance as a therapeutic option for early-stage lung cancer due to the disease's rising clinical occurrence. The treatment modality inevitably requires precise target definition and motion management, as even slight changes in planning target volume can significantly affect dosimetric quality and normal tissue sparing. This study focuses on the increasing significance of dosimetric optimization in lung stereotactic body radiation therapy with four-dimensional computed tomography and the growing implementation of magnetic resonance-guided adaptive radiation technologies in thoracic oncology, which shape new options for margin reduction and motion management. The aim of the study is to evaluate and compare the structures of the planned target volume across lung radiotherapy methods implemented with different radiotherapy equipment and to determine their impact on clinical outcomes. The work tasks include: 1) a scientific review of lung stereotactic body radiotherapy, focusing on treatment planning principles in thoracic radiotherapy; 2) evaluation and comparison of the dosimetric characteristics of lung stereotactic radiotherapy strategies; 3) analysis of differences in the planning target volume between conventional and stereotactic radiotherapy methods by developing a statistical modulation. In this study, statistical analysis methods were applied to evaluate lung stereotactic body radiotherapy planning strategies. Target volume parameters and dose-volume histogram metrics were analyzed and compared across different planning approaches using correlation and linear regression analyses. Statistical modeling methods were focused on differences in the planned target content using uniform margins and principal component analysis. Comparison between stereotactic methods and dose-volume metrics has been complicated by differing implied clinical criteria, which are more stringent in the magnetic resonance-guided adaptive radiotherapy (MRgART) strategy. However, the analysis demonstrated that a higher chest wall dose was significantly associated with increased planning target volume (PTV) maximum dose (p = 0.007), suggesting that relaxing chest wall constraints may permit greater dose escalation within the target volume. The maximum chest wall dose also showed a positive association with PTV D98% coverage, suggesting a potential trade-off between improved target coverage and increased chest wall irradiation. In contrast, Lung-GTV showed a significant negative relationship (p = 0.044) with PTV maximum dose, indicating that stricter lung dose limitations may restrict achievable target hotspot intensity. The stereotactic MRgART method, which, in a statistical modeling investigation, attained an expansion value of 24.19 at a 10 mm verge—more than double the 5 mm margin—can be seen as the most sensitive method for margin expansion. This study highlights that motion management strategies including 4D-CT, respiratory gating, and MR-guided adaptive radiotherapy are crucial for lowering motion uncertainty, minimizing PTV margins, and enhancing dosimetric precision since respiratory motion has a major impact on lung radiation planning. Moreover, stricter lung sparing seemed to restrict dose escalation within the target volume, while improved target coverage was linked to higher chest wall dose. Nonetheless, smaller target volumes showed higher relative geometric growth, according to statistical modeling, which may increase irradiation of nearby healthy lung tissue. |
