Dosimetric Evaluation of 3D-CRT and IMRT Treatment Techniques in Medulloblastoma

A primitive neuroectodermal tumor (PNET) of the cerebellum, called medulloblastoma, is an aggressive, fast-growing brain tumor.This study aims to compare the dosimetric distribution of two radiotherapy techniques-three-dimensional conformal radiation therapy (3D-CRT) and intensity-mod ulated radiation therapy (IMRT)-in patients with medulloblastoma by evaluating planning target volume (PTV) and exposure of organs at risk (OARs).In a 15-year retrospective analysis, considerable number of patients (aged 3-30 years) initially treated with 3D-CRT and subsequently with IMRT (volumetric modulated arc therapy is now used but not included in this comparison) were evaluated.Treatment plans were created in the planning system using the Monte Carlo Convolution/Superposition algorithm.Dose distributions were assessed via dose-volume histograms, and the maximum doses received by the hippocampus, brainstem, and spinal cord were compared between the two techniques.Both 3D-CRT and IMRT achieved complete coverage of the PTV.IMRT demonstrated a significant reduction in dose to critical structures, thereby lowering the risk of neurocognitive and endocrine side effects, whereas 3D-CRT delivered higher radiation levels to surrounding normal tissues.Average treatment times for IMRT were approximately 20-30% longer than for 3D-CRT.IMRT provides a more conformal dose distribution, with enhanced protection of OAR, potentially permitting higher tumor doses and improved long-term outcomes in pediatric patients.However, the choice between 3D-CRT and IMRT should be made on a case-by-case basis, taking into account the contour delineation, technical availability, and the patient's tolerance for treatment duration.(