Craniospinal irradiation by rapid Arc® technique in supine position: A dosimetric and clinical analysis

Abstract

Introduction: In craniospinal irradiation (CSI), prone position has been commonly used but, in some patients, especially pediatric cases where anesthesia is needed prone position may not help. In planning CSI by supine technique, beam geometry and field matching have to be considered, and immobilization is essential to ensure reproducibility of treatment. Materials and Methods: Data of four patients (3 with medulloblastoma and 1 with lymphoma) treated between March 2012 and October 2013 were included in this retrospective dosimetric study and analyzed. Patients were evaluated for dose coverage, organs at risks (OARs) sparing, number of monitor units, and daily table position shifts. Results: All patients underwent CSI by volumetric-modulated arc therapy (VMAT) technique in supine position. All four cases developed Grade 1 skin changes, and only one case developed a Grade 2 change at the end of radiotherapy; also both pediatric cases developed Grades 2 and 3 anemia and leukopenia toward their 4th week of treatment onward. The Rapid Arc®-CSI plans were able to generate dose distributions with high planning target volume (PTV) conformity and homogeneity and with sparing of OAR. The cumulative conformity index for all patients was 0.986, and homogeneity index was 0.1007. The mean PTV doses were within 108% with V110% of