Conservation of pyramidal tract in radiosurgery for brain metastases of lung adenocarcinoma: Three-dimensional analysis of biologically effective dose

• Published in: Radiotherapy and oncology Vol. 179; p. 109451
• Main Authors: Tang, Ke, Zhang, Nan, Yuan, Xiaodong, Qian, Zenghui, Li, Yang, Feng, Xu
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.02.2023
• Subjects: Adenocarcinoma of Lung; Biologically effective dose; Brain metastases; Brain Neoplasms - secondary; Hematology, Oncology, and Palliative Medicine; Humans; Motor function; Pyramidal tract; Pyramidal Tracts; Radiosurgery - methods; Retrospective Studies; Stereotactic radiosurgery; Three-dimensional model; Treatment Outcome; BED; Pyramidal tract; PTCF; PT; MR; CI; Biologically effective dose; VIFs; BMs; Brain metastases; HR; Three-dimensionalmodel; IQR; GKS; Stereotactic radiosurgery; CT; 3D; DTI; Motor function; magnetic resonance; Gamma Knife surgery; interquartile range; three-dimensional model; pyramidal tract conservation failure; variance inflation factors; motor function; 3-dimensional; computed tomography; brain metastases; stereotactic radiosurgery; pyramidal tract; hazard ratio; biologically effective dose; diffusion tensor imaging; confidence interval
• ISSN: 0167-8140; 1879-0887; 1879-0887
• DOI: 10.1016/j.radonc.2022.109451

Gamma knife surgery (GKS) for brain metastases (BMs) adjacent to the pyramidal tract (PT) is still a challenge to conduct. PT visualization and biologically effective dose (BED) calculation on a voxel-by-voxel basis may provide data to establish clinically safe values. We aimed to assess the relationship of parameters extracted from the BED-volume histogram with outcomes of PT after GKS-treating target (adjacent BM of lung adenocarcinoma). We formed BED-volume histograms for 672 BMs in a retrospective cohort, using 3-dimensional (3D) coordinate values of PT, target, and each iso-centre to calculate the 3D BED distribution in a 200 × 200 × 200 matrix. PT conservation failure (PTCF) was judged clinically and radiologically and classified as lesion progression and radionecrosis. Cox proportional hazards models were used to analyse 3D BED parameters. Internal validation of models was performed by bootstrapping. There were 116 (17.3 %) subjects with PTCF in the cohort, of which 74 (11.0 %) and 42 (6.3 %) were caused by lesion progression and radionecrosis, respectively. Multivariate analysis showed that DLesion_min BED and DLesion_90% BED significantly predicted lesion progression (P <.001). DPT_Max BED and VPT_ BED40 significantly predicted radionecrosis (P <.001). The model predicting PTCF showed fair discrimination and calibration of DLesion_min BED + DLesion_90% BED and DPT_Max BED + VPT_ BED40. The conservation of PT in GKS for BMs of lung adenocarcinoma depends on the combination of PT-tolerated BED and target effective control BED. Therefore, a BED-volume histogram with a 3D BED algorithm is proposed to assess plan quality.