Abstract
Purpose: Craniospinal axis irradiation (CSI) is a method of treating various central nervous system malignancies. The large target volume typically includes entire spinal cord and whole brain. Dosimetric comparison was performed between tomotherapy, volumetric modulated arc therapy (VMAT), and 3D conformal radiation therapy (3D-CRT) for CSI. Methods and Materials: Five (n = 5) CSI patients were planned using 3D-CRT, VMAT, and tomotherapy (normalized such that 95% of PTV received at least 23.4 Gy in 13 fractions). Plans were compared using PTV conformity number (CN) and homogeneity index (HI), normal tissue (NT) dose statistics, integral dose, and treatment time. Results: On average, tomotherapy plans showed higher CN (0.932 vs. 0.860 and 0.672 for SmartArc and 3D-CRT). In terms of HI, VMAT plans consistently showed better dose homogeneity (1.07 vs. 1.15 and 1.13 for tomotherapy and 3D-CRT). SmartArc delivered lower maximum dose for majority of NT, but higher mean dose. 3D-CRT plans delivered higher maximum dose but lower mean dose to NT. Conclusions: SmartArc treatments achieved better PTV homogeneity and reduced maximum dose to NT. Tomotherapy showed better target conformity, but 3D-CRT was shown to reduce mean dose to NT. Integral doses were similar between treatment modalities, but tomotherapy treatment times were much longer.
Highlights
Pediatric cases of central nervous system (CNS) tumors account for 20% - 25% of all cancer malignancies that occur in this age group of 0 - 19 years
Objectives for tomotherapy and SmartArc plans were placed on the: planning target volume (PTV), liver, heart, colon, orbits, lungs, kidneys, thyroid, and breasts for the female patients
The results indicate that the whole body integral dose is lower for the 3D conformal radiation therapy (3D-CRT) treatment technique followed by tomotherapy and SmartArc with the overall highest integral dose
Summary
Pediatric cases of central nervous system (CNS) tumors account for 20% - 25% of all cancer malignancies that occur in this age group of 0 - 19 years. Of these pediatric CNS tumors, medulloblastoma accounts for 15% - 20% of occurrences [1]. Craniospinal irradiation (CSI) is a necessary method of treatment for many CNS malignancies. Along with a boost to the posterior fossa and chemotherapy, this CSI treatment allows for a five-year survival of 80% or better [2,3]. In order to minimize these future complications and better the long-term outcome for medulloblastoma
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