Craniospinal Irradiation Using Three-Dimensional Conformal Radiotherapy with Two Different Planning Techniques: A Comparative Analysis in Supine and Prone Positions

Abstract

Objectives: Craniospinal Irradiation (CSI) requires radiotherapy delivery to the entire neuraxis. It is accomplished by using multiple overlapping beams covering the large target volume, which are then matched to one another using collimation, couch rotation or beam modifications. Although modern radiotherapy techniques like Intensity Modulated Radiotherapy (IMRT) and Proton Beam Therapy (PBT) offer significant advantages in delivering CSI, yet 3-Dimensional Conformal Radiotherapy (3DCRT) remains the primarily used technique- more so in resource constrained settings. Materials and Methods: The CT simulation datasets of six patients (3 supine and 3 prone positions) were used for planning two different techniques for CSI: A) Two isocenter plan with half beam block and no collimator rotation (2iso-HB-WOC) and B) Three isocenter plan with half beam block and collimator rotation (3iso-HB-WC). Plans were compared using Dose Volume Histogram (DVH) parameters for Planning Target Volume (PTV) and Organs at Risk (OARs). Results: Considering dosimetric parameters, the 2iso-HB-WOC technique was found to be equivalent to 3iso-HB-WC technique in terms of PTV coverage and OAR doses. However, on evaluating treatment positions, the volume of hotspots (V107%) was significantly lesser [Mean: 141.83cc vs 243.50cc, p=0.02] with improved minimum dose (Dmin) in PTV [Mean: 29.68Gy vs 14.49Gy, p=0.03] for supine than in prone position. Also, the maximum point dose (Dmax) to the mandible was significantly lower in patients treated in supine position [37.0Gy vs 31.31Gy, p=0.01]. Conclusion: We suggest 2iso-HB-WOC technique for delivering CSI with 3DCRT. Also, supine positioning of patients in CSI appears to be dosimetrically advantageous.