Transition from 3D conformal to modern modulated craniospinal radiotherapy

Background: Achieving optimal tumour coverage during craniospinal irradiation (CSI) is a challenge. Whilst several critical organs are at risk of radiation-induced toxicity, if target volume structures like the cribriform plate receive less than 95% of the prescribed dose, tumours could recur.Aim: This single-institution study seeks to establish the most effective craniospinal radiotherapy amongst 3D conformal radiation therapy (CRT), intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) by comparing dosimetry across target volumes, organs at risk (OARs) and total irradiated volume. Time taken for contouring, generation and evaluation of treatment plans, quality assurance and treatment beam delivery is assessed.Setting: The demographics of patients comprised of six children and one adult who underwent 3D CRT craniospinal radiotherapy at a Western Cape hospital.Methods: Approval from the Human Research Ethics Committee was obtained. The 3D CRT plan consisted of two parallel opposing lateral fields at the cranial isocentre and a single posterior field at the spinal isocentre. Both the IMRT and VMAT plans comprised three isocentres, one cranial and two spinal, with a total of 15 fields.Results: Volumetric modulated arc therapy was the most conformal (CI = 0.48) and IMRT the most homogeneous (HI = 0.06). Although the VMAT low-dose bath (58.1%) was highest at 2 Gy, OARs were least exposed with VMAT. The total time taken for VMAT was the shortest.Conclusion: Volumetric modulated arc therapy was recommended as the most effective CSI technique owing to its superior conformality, least OARs exposure and fastest planning times. Clinical investigation into possible late adverse effects arising from the VMAT low-dose bath should be conducted.Contribution: This study will establish which of the three radiation therapy (RT) techniques is most effective in the treatment of craniospinal tumours, as well as, which technique offers the fastest turn around time.