Dosimetric comparison of IMRT, VMAT, and hybrid techniques in stereotactic body radiotherapy for adrenal metastases

Stereotactic body radiotherapy (SBRT) has emerged as a non-invasive alternative for the treatment of adrenal metastases, increasingly replacing traditional invasive approaches. However, its clinical application remains under investigation. The introduction of advanced radiotherapy techniques has further fueled interest in SBRT, necessitating comprehensive dosimetric evaluations to optimize treatment strategies. This study compares three distinct SBRT techniques: pure intensity-modulated radiotherapy (IMRT), pure volumetric modulated arc therapy (VMAT), and a hybrid approach combining VMAT and IMRT, utilizing flattening filter-free (FFF) photon beams. Treatment plans were assessed using dosimetric distributions, dose-volume histograms (DVH), homogeneity index (HI), and conformity index (CI). Repeated-measures analysis of variance (ANOVA) was performed, with statistical significance set at p < 0.05. Both VMAT and hybrid plans demonstrated superior CI and HI values compared to IMRT. However, the maximum dose (Dmax) to the planning target volume (PTV) was lower in the hybrid plan than in VMAT but comparable to IMRT. Additionally, critical organ dose analyses revealed that VMAT and hybrid plans achieved significantly lower doses in the renal cortex (Dmax and V17.5), duodenum (Dmax and V12.5), aorta (Dmax), and stomach (Dmax) compared to IMRT. The findings indicate that both VMAT and hybrid techniques outperform IMRT, offering improved plan quality and superior critical organ sparing. These results highlight the potential clinical advantages of VMAT and hybrid SBRT approaches in the treatment of adrenal metastases. Further clinical validation through large-scale studies is warranted to establish the optimal treatment strategy.